- Dr Paul J. Vardanega joined the University of Bristol in September 2013 as a Lecturer in Civil Engineering. He then s... moreDr Paul J. Vardanega joined the University of Bristol in September 2013 as a Lecturer in Civil Engineering. He then served as a Senior Lecturer in Civil Engineering from August 2018 to July 2021 at the same institution. Since August 2021 he has been an Associate Professor in Civil Engineering also at the University of Bristol.edit
This note presents the application of the mobilisable strength design (MSD) method to the monitoring results of the multipropped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff... more
This note presents the application of the mobilisable strength design (MSD) method to the monitoring results of the multipropped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff clay deposit. The MSD method is an energy-based approach (a nonlinear finite-element method for a single-degree-of-freedom soil-wall system) introduced to develop a simplified design methodology that satisfies both ultimate and serviceability limit states. Wall displacement predictions based on the MSD method are compared with considerable field monitoring data. The sensitivity of the method to reasonable variations in input parameters is considered. A spreadsheet and python code demonstrating the MSD analysis from this paper are provided in the online supplement alongside details of the mathematical formulation.
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The visual inspection of bridges is a major undertaking for asset owners and operators. In the UK, visual inspections require inspectors to visit bridges on-site and often at night and in unfavourable weather conditions. Therefore, it... more
The visual inspection of bridges is a major undertaking for asset owners and operators. In the UK, visual inspections require inspectors to visit bridges on-site and often at night and in unfavourable weather conditions. Therefore, it would be beneficial to move some of the visual inspection process off-site. This paper studies whether the defect classification aspects of the inspection process could be conducted remotely using photographs. This study examines the defect ratings assigned by ten survey participants who were tasked with examining photographs from visual inspections of ten UK bridges. The survey results were compared with the results from the general inspections previously carried out for the bridges in question. From this dataset, the differences in the ratings given and the extent to which defects are missed were examined. The results show that a higher number of defects were identified for a given bridge by the remote inspectors. Statistical analysis shows that aggregated defects rated by off-site inspectors tend to be more severe and of a higher priority rating compared to those from the on site inspectors. The results also indicate that there is closer agreement between on-site and off-site inspectors for defects of a higher severity rating.
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Visual inspection remains key for assessing the condition of bridges and hence assisting with planning and maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing... more
Visual inspection remains key for assessing the condition of bridges and hence assisting with planning and
maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing technologies and data capture methods to usher in an era of ‘smart bridges’ or ‘smart infrastructure’. One method to improve data capture is a ‘remote inspection’ where inspectors use digital photographs of a bridge to identify and grade structural defects to the standard of a ‘general inspection’. In this paper, survey data are presented to help formulate a preliminary assessment of the potential for engineers to implement this possible evolution of the visual inspection process. A potential schema for remote visual inspections is developed and presented as a conceptual web application. The focus on the development of the schema includes the need for ease of use by inspectors and integration of collected digital data into bridge management systems. The suggested platform is seen as a transitional method to aid in the long-term implementation of further automation of the inspection process. The system architecture is provided along with possible technologies that may support or enhance it, as well as a discussion of the potential barriers to implementation.
maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing technologies and data capture methods to usher in an era of ‘smart bridges’ or ‘smart infrastructure’. One method to improve data capture is a ‘remote inspection’ where inspectors use digital photographs of a bridge to identify and grade structural defects to the standard of a ‘general inspection’. In this paper, survey data are presented to help formulate a preliminary assessment of the potential for engineers to implement this possible evolution of the visual inspection process. A potential schema for remote visual inspections is developed and presented as a conceptual web application. The focus on the development of the schema includes the need for ease of use by inspectors and integration of collected digital data into bridge management systems. The suggested platform is seen as a transitional method to aid in the long-term implementation of further automation of the inspection process. The system architecture is provided along with possible technologies that may support or enhance it, as well as a discussion of the potential barriers to implementation.
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Scour is a significant cause of bridge failure, and resulting bridge closures are likely to generate significant disruption to infrastructure networks. The management of scour-susceptible bridges is a significant challenge for improving... more
Scour is a significant cause of bridge failure, and resulting bridge closures are likely to generate significant disruption to infrastructure networks. The management of scour-susceptible bridges is a significant challenge for improving transport resilience, but tends to be heuristic and qualitative. Such assessments often suffer from insufficient knowledge of key factors and require assumptions, which may increase their estimation and relative uncertainty. Analysis of publicly available technical documents reveals that various definitions of “risk” are adopted, as well as multiple approaches are applied. This paper has three objectives: (i) to illustrate the concept of risk in bridge scour management; (ii) to propose a simple scoring system to analyse existing risk-based approaches to manage bridge scour; and (iii) to analyse and compare such approaches on the basis of the obtained scores. A sample of nine documents containing bridge scour risk assessment practices or approaches was analysed using the developed rating system.
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This paper presents laboratory data from tests on four fine-grained soils: reconstituted Kaolinite, destructured Bothkennar clay, reconstituted Bothkennar clay, and reconstituted Gault clay. The soil samples were conditioned in an... more
This paper presents laboratory data from tests on four fine-grained soils: reconstituted Kaolinite, destructured Bothkennar clay, reconstituted Bothkennar clay, and reconstituted Gault clay. The soil samples were conditioned in an oedometer cell while being subjected to varying numbers of freezing and thawing cycles. The influence of freeze-thaw cycles on key soil parameters, including the hydraulic conductivity, Atterberg limits, compression and swelling index was studied. The experimental results were then compared with the analysis of a previously published database of hydraulic conductivity measurements on fine-grained soils called FG/KSAT-1358. The paper demonstrates that while multiple cycles of freezing and thawing affect some of the studied soil parameters, such as the Atterberg limits and the compression characteristics, the effects on the hydraulic conductivity transformation model parameters, linking the water content ratio to hydraulic conductivity are less apparent. The results are useful for geotechnical and pavement engineers when making assessments of freeze-thaw effects on subgrade materials in cold regions.
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This paper reviews commonly used parameters and prediction models for assessing the permeability of granular soils. Following a review of published models for prediction of soil permeability, a dimensional homogenous transformation model... more
This paper reviews commonly used parameters and prediction models for assessing the permeability of granular soils. Following a review of published models for prediction of soil permeability, a dimensional homogenous transformation model for a-priori estimation of soil permeability was calibrated using a large database (CG/ KSAT/7/1278) comprising permeability data for a wide range of granular soils sourced from over 50 publications. The new transformation model requires knowledge of the void ratio and gradation of the material to make estimates of the soil permeability. The prediction accuracy of the calibrated model was then assessed alongside that of other empirical and semi-empirical models also calibrated using CG/KSAT/7/1278. The potential influences of void ratio, key gradation parameters and permeability test type on the prediction accuracy of the proposed model are also examined. The paper shows that while the fitted constants in the proposed transformation model are affected to varying extents by the aforementioned parameters, it does offer reasonable predictions of permeability with only knowledge of the void ratio and material gradation required.
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The UK has a large stock of highway bridges that is ageing and deteriorating. This paper presents the results of a programme of work to understand the reliability of the visual inspection data that are used to inform the management of... more
The UK has a large stock of highway bridges that is ageing and deteriorating. This paper presents the results of a programme of work to understand the reliability of the visual inspection data that are used to inform the management of Highways England’s structures. This paper presents a data set comprising evidence collected during the presence of research team inspectors at the principal inspection and/or testing of 200 bridges randomly sampled from Highways England’s bridge network, coupled with asset-management data for Highways England’s entire bridge stock. Recommendations are made for future improvements in visual inspection practice and use of such data in future asset-management efforts.
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The availability of reliable field data is critical for the advancement of geotechnical engineering. This is particularly the case for piled foundations; due to the substantial geotechnical uncertainties. The settlement (performance)... more
The availability of reliable field data is critical for the advancement of geotechnical engineering. This is particularly the case for piled foundations; due to the substantial geotechnical uncertainties. The settlement (performance) predictions from established analytical methods may deviate from field measurements by as much as an order of magnitude. This paper provides a statistical assessment of the uncertainty of predictions of pile performance under axial loading using an openly accessible geotechnical database of pile load tests from the United Kingdom. The collected database information was classified by pile type, location, test data quality and availability of geotechnical data. With reference to the data from fine-grained soils, two analytical models were employed to predict foundation settlement. The settlement prediction performance was then studied statistically and the model bias and error compared with reference to the aforementioned categories to identify the impact of different sources of uncertainty and evaluate the use of both models for future geotechnical practice. The two models investigated generally over-predict settlement, which is likely due to conservative selection of key model parameters, such as soil strength.
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Estimation of nonlinear pile settlement can be simplified using one-dimensional "t-z" curves that conveniently divide the soil into multiple horizontal "slices." This simplification reduces the continuum analysis to a two-point... more
Estimation of nonlinear pile settlement can be simplified using one-dimensional "t-z" curves that conveniently divide the soil into multiple horizontal "slices." This simplification reduces the continuum analysis to a two-point boundary-value problem of the Winkler type, which can be tackled by standard numerical procedures. Theoretical "t-z" curves can be established using the "shearing-of-concentric cylinders" theory of Cooke and Randolph-Wroth, which involves two main elements: (1) a constitutive model cast in flexibility form, γ =γ(τ); and (2) an attenuation function of shear stress with radial distance from the pile, τ =τ(r). Soil settlement can then be determined by integrating shear strains over the radial coordinate, which often leads to closed-form solutions. Despite the simplicity and physical appeal of the method, only a few theoretical "t-z" curves are available in the literature. This paper introduces three novel attenuation functions for shear stresses, inspired by continuum solutions, which are employed in conjunction with eight soil constitutive models leading to a set of 32 "t-z" curves. Illustrative examples of pile settlement calculation in two soil types are presented to demonstrate application of the method.
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Use of the Casagrande-style plasticity chart to classify fine-grained soils using Atterberg’s liquid and plastic limits is ubiquitous in geotechnical engineering. This classification is dependent on the thread-rolling and Casagrande-cup... more
Use of the Casagrande-style plasticity chart to classify fine-grained soils using Atterberg’s liquid and plastic limits is ubiquitous in geotechnical engineering. This classification is dependent on the thread-rolling and Casagrande-cup tests, which are both more operator dependent than the fall-cone liquid limit test. This paper shows that the slope of the data acquired during the fall-cone liquid limit test (the fall-cone flow index) can be used to redraw the plasticity chart, thus allowing classification of fine-grained soils to be achieved solely from fall-cone liquid limit data.
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During bridge design and assessment, effects of thermal actions are accounted for by means of a uniform temperature variation and temperature difference components. The uniform temperature variations cause changes in length and width of... more
During bridge design and assessment, effects of thermal actions are accounted for by means of a uniform temperature variation and temperature difference components. The uniform temperature variations cause changes in length and width of the structure, whereas the temperature difference components primarily cause curvatures and internal stresses. The effects of these strains on the superstructure depend on the structure's articulation and restraint. Design profiles used to model the temperature difference components vary between design codes, which can have a significant effect on the induced curvatures. Thermal data findings obtained from a comprehensive, year-long monitoring programme on Waterloo Bridge in London are examined, which allows comparison of these various models with performance data. The design thermal model in BS EN 1991-1-5 is examined, supplemented by the models from the AASHTO and New Zealand codes. The measured uniform bridge temperature generally fell within the stipulated limits of BS EN 1991-1-5; however, at low temperatures the minimum deck temperature may be lower than the design relationship provided. The resultant moments implied from the measured vertical profiles: significantly exceed the worst-case values predicted by the UK model; exceed the AASHTO model at different bridge sections; and do not exceed the New Zealand model.
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An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole... more
An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole datapoints (published in SAFER/GEO-591) were used to compare two methods for the estimation of liquefaction potential. Standard Penetration Test (SPT) blowcount data from 75 boreholes inform the new liquefaction potential maps. Various scenarios were modelled, i.e., seasonal variation of the groundwater table and peak ground acceleration. Ordinary kriging, implemented in ArcGIS, was used to prepare maps at urban scale. Liquefaction potential calculations using the methodology from (Sonmez, Environ Geol 44:862-871, 2003) provided a good match to the historical liquefaction records in the region. Seasonal variation of the groundwater table is shown to have a significant effect on the spatial distribution of calculated liquefaction potential across the valley. The less than anticipated liquefaction manifestations due to the Gorkha earthquake are possibly due to the seasonal water table level.
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Bridge scour is a complex bridge-management problem. It is also a difficult forensic engineering challenge, as the greatest risk occurs during large flows and flood events, when visual inspection of the bridge piers is often not possible.... more
Bridge scour is a complex bridge-management problem. It is also a difficult forensic engineering challenge, as the greatest risk occurs during large flows and flood events, when visual inspection of the bridge piers is often not possible. This paper presents a review of scour prediction and modelling methods, whose results are used to determine the key parameters that scour-monitoring systems need to capture. Then, a review of existing monitoring approaches and technologies for scour monitoring is presented. The paper concludes with the proposal of a novel rating system for evaluating different scour-monitoring techniques. The new rating system is trialled ex-post for seven previously published bridge-scour-monitoring case studies to illustrate the use of the new methodology.
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Aerial robotic technology has potential for use in a wide variety of civil engineering applications. Such technology potentially offers low-cost methods to replace expensive structural health monitoring activities such as visual... more
Aerial robotic technology has potential for use in a wide variety of civil engineering applications. Such technology potentially offers low-cost methods to replace expensive structural health monitoring activities such as visual inspection. Aerial robots also have potential uses in civil construction and for regional surveys. This paper presents the results of a review on the applications of aerial robotic technology in civil engineering. Such civil engineering applications can be classified into three broad areas: (i) monitoring and inspection of civil infrastructure; (ii) site management, robotic construction, and maintenance; and (iii) post-disaster response surveys and rapid damage assessments. The motivations for uptake of aerial robotics in the civil engineering industry generally fall into the following categories: (i) cost savings, (ii) improved measurement capability, and (iii) safety improvements. The categories of aerial robotic use in civil engineering are then classified as either “established” or “emerging” uses.
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Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate the cyclic resistance ratio (CRR) and for the evaluation of in situ soil behavior. This article presents CPTu data acquired in the Kathmandu... more
Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate the cyclic resistance ratio (CRR) and for the evaluation of in situ soil behavior. This article presents CPTu data acquired in the Kathmandu valley sediments and makes use of established CPTu interpretation procedures to assess the soil in situ properties. Up to this point predominantly SPT data and limited shear wave velocity measurements have been relied upon to assess the variability and seismic response of soil deposits underlying Kathmandu. This article provides 1) additional data to add to the existing SAFER/GEO-591 database, 2) new shear-wave velocity measurements, and 3) initial estimates of CRR at the sites visited. Based on the work presented in this article, it is concluded that a more detailed methodology is needed for liquefaction assessment mainly due to the presence of saturated silts in the valley.
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Geostatistical methods are valuable to better understand the spatial distribution of geotechnical parameters at regional scale and to optimize the locations of future ground investigations. This article investigates the use of the kriging... more
Geostatistical methods are valuable to better understand the spatial distribution of geotechnical parameters at regional scale and to optimize the locations of future ground investigations. This article investigates the use of the kriging interpolation method to extend the knowledge of a specific geotechnical property from a few sites to a broader geographical area with a focus on the Kathmandu valley (Nepal). A Bayesian form of kriging is proposed in this article. The estimation of the shear wave velocity in the uppermost 30 m of soil (V S30) in the Kathmandu valley is examined. Slope-based V S30 estimates from the United States Geological Survey are used as prior information, and 15 V S30 measurements are used as more precise data. Considering the limited number of high-quality V S30 measurements available in the valley, it is shown that the Bayesian scheme can lead to a more robust estimation of V S30 than that obtained with the ordinary kriging approach. A methodology for conditioning prior low-precision data to the measurements is also presented.
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The sharing of ground investigation (GI) data within the UK is commonly practised only in large infrastructure projects. A vast amount of GI data collected on routine projects is commonly not made publicly available which is arguably... more
The sharing of ground investigation (GI) data within the UK is commonly practised only in large infrastructure projects. A vast amount of GI data collected on routine projects is commonly not made publicly available which is arguably inefficient and potentially unsustainable. This paper captures the opinions of the geoscience community and the GI industry on data sharing to better understand current working practices and potential barriers to data sharing. The results of a survey carried out at the Janet Watson Meeting 2018: A Data Explosion: The Impact of Big Data in Geoscience held at the Geological Society of London are reported. This survey is compared with the results of interviews undertaken during the Dig to Share project, a collaborative project led by Atkins, British Geological Survey (BGS) and Morgan Sindall. The opinions and practices of geoscientists towards data sharing across a project life cycle are reviewed. Drivers of risk relating to geotechnical aspects of a project are directly linked to current data sharing practice.
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A new database called AC/k-1624 containing over 1600 measurements of saturated hydraulic conductivity of asphalt concrete has been assembled and analysed. AC/k-1624 was used to investigate the effect of the grading entropy parameters on... more
A new database called AC/k-1624 containing over 1600 measurements of saturated hydraulic conductivity of asphalt concrete has been assembled and analysed. AC/k-1624 was used to investigate the effect of the grading entropy parameters on saturated hydraulic conductivity. A new prediction model comprising both air voids and grading entropy is presented. The database analysis using different predictors of asphalt hydraulic conductivity reveals that the gradation does affect the hydraulic conductivity, but the air void level is necessary to make reasonable a-priori assessments of hydraulic conductivity for asphalt concrete. The new empirical model is shown to have a good predictive capacity for hydraulic conductivity fitting more securely at higher values with more scatter observed at lower values. The effects of test type, gradation classification and Nominal Maximum Aggregate Size (NMAS) are also studied, revealing in general relatively modest influences on the computed regression coefficients.
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Considerable amounts of data are collected on the UK’s stock of bridges. Much of this data is collected to inform the planning and scope of maintenance activities. This paper reports on the results of a series of semi-structured... more
Considerable amounts of data are collected on the UK’s stock of bridges. Much of this data is collected to inform the planning and scope of maintenance activities. This paper reports on the results of a series of semi-structured interviews with 17 individuals involved in UK bridge asset management and data-collection activities to explore how such data is used in practice. A wide spectrum of organisations and industrial sectors was represented in this dataset. Hierarchical process modelling was used to characterise the UK’s bridge management system and define the processes and sub-processes involved in the management of bridges. Key quotations are used from the interviews to reveal the state of data collection and use in UK bridge infrastructure from the perspective of those directly involved. The study concludes that there is significant variation within the industry regarding the use of visual inspection data and that formal structural health monitoring remains relatively rare. Furthermore, there is a need to develop a new unifying paradigm that will frame the efficient and effective application of emerging artificial intelligence and data science enabled (i.e. ‘smart’) condition-monitoring techniques to bridge management.
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The Kathmandu Valley is within a seismically active region with only few recorded strong-motion data. Geophysical information in the Valley is also sparse. In addition, the absence of an open database which compiles in situ geophysical... more
The Kathmandu Valley is within a seismically active region with only few recorded strong-motion data. Geophysical information in the Valley is also sparse. In addition, the absence of an open database which compiles in situ geophysical tests, borehole records, and geotechnical laboratory data is affecting the advancement of knowledge in the region. This article presents SAFER/GEO-591 database, named after the Engineering and Physical Science Research Council (EPSRC)-funded project Seismic Safety and Resilience of Schools in Nepal (SAFER). SAFER/GEO-591 contains data from groundwater wells and boreholes originally commissioned for research and commercial purposes. This work describes (1) the quality assessment and harmonization process conducted on the dataset, (2) the variation of shear-wave velocity (VS) measurements and geotechnical parameters with depth and elevation in the Valley, (3) the current understanding of the Valley sediment/bedrock topography, and finally (4) new geological cross sections. A companion article presents an updated VS30 map across the Valley based on the contributions of this article. The database can be downloaded from the University of Bristol repository via DOI: https://doi.org/10.5523/bris.3gjcvx51lnpuv269xsa1yrb0rw
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During construction, the mobilisation of undrained shear strength must be limited to avoid soil failure. Soil strains must be controlled to avoid compromising structural serviceability. To assess foundation performance by strength... more
During construction, the mobilisation of undrained shear strength must be limited to avoid soil failure. Soil strains must be controlled to avoid compromising structural serviceability. To assess foundation performance by strength mobilisation, an understanding of soil strains at various levels of strength mobilisation is required. In practice, ground investigation data is often limited, and assessment of the expected variation of stress-strain and undrained shear strength is improved with empirical correlations calibrated with a database. The new database RFG/TXCU-278 contains data of 278 consolidated undrained triaxial tests on reconstituted fine-grained soil samples compiled from the literature. Analysis of the database to evaluate the variability of undrained strength ratio (cu /σ'v0) and a reference shear strain with shear mode is undertaken in this paper. The new database provides evidence that shear strain (like undrained shear strength) is sensitive to the consolidation (isotropic or K0) and shear mode (triaxial compression or extension) applied in the test. For the materials included in the database, the strength mobilisation parameters obtained from a triaxial compression test can be used to predict the corresponding triaxial extension parameters to a reasonable accuracy.
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Many real-world applications have been suggested in the swarm robotics literature. However, there is a general lack of understanding of what needs to be done for robot swarms to be useful and trusted by users in reality. This paper aims... more
Many real-world applications have been suggested in the swarm robotics literature. However, there is a general lack of understanding of what needs to be done for robot swarms to be useful and trusted by users in reality. This paper aims to investigate user perception of robot swarms in the workplace, and inform design principles for the deployment of future swarms in real-world applications. Three qualitative studies with a total of 37 participants were done across three sectors: fire and rescue, storage organization, and bridge inspection. Each study examined the users' perceptions using focus groups and interviews. In this paper, we describe our findings regarding: the current processes and tools used in these professions and their main challenges; attitudes toward robot swarms assisting them; and the requirements that would encourage them to use robot swarms. We found that there was a generally positive reaction to robot swarms for information gathering and automation of simple processes. Furthermore, a human in the loop is preferred when it comes to decision making. Recommendations to increase trust and acceptance are related to transparency, accountability, safety, reliability, ease of maintenance, and ease of use. Finally, we found that mutual shaping, a methodology to create a bidirectional relationship between users and technology developers to incorporate societal choices in all stages of research and development, is a valid approach to increase knowledge and acceptance of swarm robotics. This paper contributes to the creation of such a culture of mutual shaping between researchers and users, toward increasing the chances of a successful deployment of robot swarms in the physical realm.
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This paper presents experimental investigations on the feasibility of using a sand-rubber deformable granular layer as a low-cost seismic isolation strategy for developing countries. The mechanical characteristics of a potential failure... more
This paper presents experimental investigations on the feasibility of using a sand-rubber deformable granular layer as a low-cost seismic isolation strategy for developing countries. The mechanical characteristics of a potential failure mechanism inside the sand-rubber layer are investigated. Direct shear testing is performed to quantify the angle of friction of three different sand-rubber mixtures subjected to different vertical stress levels. The experimentally derived mechanical characteristics are compared to the corresponding values for pure rubber and pure sand samples. The frictional characteristics of sliding between a sand-rubber layer and a timber interface are identified. Direct shear testing is performed to quantify the quasi-static friction of the same sand-rubber mixtures against a timber interface, that is part of the foundation casting, subjected to alternative vertical stresses. The effect of the shear rate and the saturation of the sand-rubber mixture on the aforementioned mechanical characteristics is presented. A uniaxial shaking table experimental setup is used for the investigation of the dynamics of a rigid sliding block and the quantification of the kinetic friction of different sliding interfaces against two different sand-rubber mixtures for two different sand-rubber layer heights. The rigid sliding block designed to slide against the sand-rubber layer is subjected to both a harmonic ramp loading and earthquake ground motion excitation. The design outcome of this static and dynamic experimental investigation is the determination of the optimum grain size ratio and the height of the sand-rubber layer, that corresponds to the lower (and more favourable from a seismic isolation view point) friction coefficient between the sand-rubber layer and the foundation. The quantification of these fundamental parameters paves the way for a holistic design of a response modification strategy for mitigating seismic damage in developing countries.
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Identification of failure thresholds and critical uncertainties associated with slope stability often requires the specification of geotechnical parameter values for input into a physically-based model. The variation of these parameters... more
Identification of failure thresholds and critical uncertainties associated with slope stability often requires the specification of geotechnical parameter values for input into a physically-based model. The variation of these parameters (including mechanical soil properties such as effective friction angle and cohesion) can have a significant impact on the computed factor of safety. These uncertainties arise from natural variations in soils, measurement techniques, and lack of reliable information. Researchers may use statistical analysis coupled with numerical simulation to determine possible ranges of slope factors of safety and the relative influence of geotechnical and other parameters, such as topsoil depth and rainfall. This study investigates the variation of geotechnical parameters observed on the island of Saint Lucia in the Eastern Caribbean. A database of particle size distributions, in-situ moisture contents, Atterberg and direct shear box test results is compiled from 91 samples of tropical soils in Saint Lucia. A study of various probability distributions shows that the Weibull distribution may be favoured for the effective friction angle of the Saint Lucian soils considered based on the Akaike information criterion, employed as an estimator of the relative quality of statistical models dealing with the trade-off between goodness-of-fit and simplicity of the model.
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This note presents some constant-head permeability test results on 30 granular mixtures. These data are then interpreted using the grading entropy approach, as well as the ‘Hazen’, ‘Shepherd’, ‘Kozeny–Carman’ and ‘Chapuis’ models. The... more
This note presents some constant-head permeability test results on 30 granular mixtures. These data are then interpreted using the grading entropy approach, as well as the ‘Hazen’, ‘Shepherd’, ‘Kozeny–Carman’ and ‘Chapuis’ models. The predictive power of each of the five methods is compared. A correlation between the normalised grading entropy coordinates and the coefficient of permeability is presented. Permeability zones on the normalised entropy diagram are identified.
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This paper reports the results of 120 low-cycle fatigue tests on steel reinforcing bars with varying slenderness ratios at varying strain amplitudes. The failure modes of the fractured bars were investigated through analysis of the... more
This paper reports the results of 120 low-cycle fatigue tests on steel reinforcing bars with varying slenderness ratios at varying strain amplitudes. The failure modes of the fractured bars were investigated through analysis of the fracture mechanisms of bars. The results of experimental testing were used to update empirical models of low-cycle fatigue life for such bars. The newly improved empirical models were then incorporated into a recently developed constitutive material model that accounts for bar buckling and fatigue. The experimental results show that the size effect is significant for short steel reinforcing bars where there is no buckling. The results also show that as the slenderness ratio of the steel reinforcing bars increases, the influence of the bar diameter on low-cycle fatigue reduces.
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Road construction in peatlands is challenging. The ability to make rapid estimates of the response of construction soils derived from natural peats to changes in water content is useful for pavement and geotechnical engineers. This paper... more
Road construction in peatlands is challenging. The ability to make rapid estimates of the response of construction soils derived from natural peats to changes in water content is useful for pavement and geotechnical engineers. This paper details some laboratory test results on peat soils sourced from two sites in the Southwest of England. The samples were sieved and the roots and natural fibres removed prior to laboratory testing. Water contents on the natural specimens were determined. The percentage of roots in the samples was determined. The thread rolling test was used to estimate the plastic limit of the peat soil material. A series of fall cone tests were conducted at varying moisture contents to determine the liquid limit of the peat soil as well as study the variation of fall cone undrained shear strength with the liquidity index, logarithmic liquidity index and the water content ratio. Both the liquidity index and logarithmic liquidity index are able to predict the fall cone undrained strength to within ± 40% around 90% of the time. When using the water content ratio to predict the fall cone undrained shear strength an accuracy of ± 40% is achieved around 85% of the time. The study concludes that the liquidity index and logarithmic liquidity index are better predictors of fall cone undrained shear strength but the water content ratio approach may be preferred if the engineer is less confident in plastic limit determination for peat soils.
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Corrigendum to 'Use of fall cones to determine Atterberg limits: a review'
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This paper reviews the percussion-cup liquid limit, thread-rolling plastic limit (PL) and various fall-cone and other approaches employed for consistency limit determinations on fine-grained soil, highlighting their use and misuse for... more
This paper reviews the percussion-cup liquid limit, thread-rolling plastic limit (PL) and various
fall-cone and other approaches employed for consistency limit determinations on fine-grained soil,
highlighting their use and misuse for soil classification purposes and in existing correlations. As the PL
does not correspond to a unique value of remoulded undrained shear strength, there is no scientific
reason why PL measurements obtained using the thread-rolling and shear-strength-based fall-cone or
extrusion methods should coincide. Various correlations are established relating liquid limit values
deduced using the percussion-cup and fall-cone approaches. The significance of differences in the
strain-rate dependency on the mobilised fall-cone shear strength is reviewed. The paper concludes with
recommendations on the standardisation of international codes and the wider use of the fall-cone
approach for soft to medium-stiff clays in establishing the strength variability with changing water
content and further index parameters.
fall-cone and other approaches employed for consistency limit determinations on fine-grained soil,
highlighting their use and misuse for soil classification purposes and in existing correlations. As the PL
does not correspond to a unique value of remoulded undrained shear strength, there is no scientific
reason why PL measurements obtained using the thread-rolling and shear-strength-based fall-cone or
extrusion methods should coincide. Various correlations are established relating liquid limit values
deduced using the percussion-cup and fall-cone approaches. The significance of differences in the
strain-rate dependency on the mobilised fall-cone shear strength is reviewed. The paper concludes with
recommendations on the standardisation of international codes and the wider use of the fall-cone
approach for soft to medium-stiff clays in establishing the strength variability with changing water
content and further index parameters.
Research Interests:
Asset management organisations collect large quantities of data on the inventory, condition and maintenance of their bridge structures. A key objective in the collection of these asset data is that these can be processed into useful... more
Asset management organisations collect large quantities of data on the inventory, condition and maintenance of their bridge structures. A key objective in the collection of these asset data is that these can be processed into useful information that can inform best practice for the design of new structures and the management of existing stocks. As a leading bridge asset owner, Highways England, UK, is applying insights from mining of its asset data to contribute to continual improvement in the management of structures and its understanding of their performance. This paper presents the application of modern data science tools and optimal decision tree learning to Highways England's asset information database comprising bridge inventory, inspection records and historic and current defects for its stock of thousands of bridges. Trends are observed in the factors affecting the current condition of bridges and their rate of deterioration. Optimal decision trees are used to identify the most influential factors in the performance of bridge structures and present complex multifactor trends in a format readily digested by managers and decision makers, to inform standards and policy.
Prediction of the conditions under which landslides may occur is essential for designing sustainable risk-mitigation measures and cost-effective geotechnical structures. Slope stability analyses typically account for slope geometry, soil... more
Prediction of the conditions under which landslides may occur is essential for designing sustainable risk-mitigation measures and cost-effective geotechnical structures. Slope stability analyses typically account for slope geometry, soil mechanical properties and groundwater conditions to determine the performance of a slope with respect to a specified factor of safety. These properties vary both spatially and over time; geotechnical design codes require the use of factored design parameter values to account for possible worst-case conditions. Furthermore, standard geotechnical analyses typically exclude the dynamic hydrological processes of rainfall infiltration and loss of matric suction that often trigger landslides. Slope stability assessment is particularly challenging in developing countries with limited resources for acquiring slope data, meeting conservative design standards and mitigating landslide risk. This study applied a combined slope hydrology and stability model to address these issues for a residual soil slope in the tropics. This paper presents a method for maximising stability information from limited data, disaggregating the effects of three different design parameter sets and factor of safety threshold choices, as well as diagnosing the dominant geotechnical and dynamic landslide-triggering factors. This modelling approach provides a more transparent basis for sustainable slope-management decisions.
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The Clifton Suspension Bridge is an emblematic structure in Bristol, UK. In this paper, a rapid deployment of a structural health monitoring (SHM) system for short-term monitoring is described. The system, deployed in a single day,... more
The Clifton Suspension Bridge is an emblematic structure in Bristol, UK. In this paper, a rapid deployment of a structural health monitoring (SHM) system for short-term monitoring is described. The system, deployed in a single day, integrates wireless SHM and open-source data management systems to gather valuable information about the bridge use (loading). The deployed system can be used to inform structural response models as well as studies for traffic engineering purposes. The use of open-source software was critical to the successful deployment.
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Among current approaches for fatigue strength assessment, the effective notch stress method is widely employed by practising engineers designing welded joints. This is particularly important in the situation where the nominal stress and... more
Among current approaches for fatigue strength assessment, the effective notch stress method is widely employed by practising engineers designing welded joints. This is particularly important in the situation where the nominal stress and structural stress cannot be easily quantified. In this paper, the applicability of the so called effective notch stress approach on large-size T-joints in truss bridges is investigated through a comprehensive experimental programme supported by numerical analysis. A series of large-scale fatigue tests on prototype large-size T-joints with cope holes were conducted. These types of joints are normally used in fully welded truss bridges. Furthermore , a simple parametric study was conducted using finite element analysis to investigate the effect of plate thickness and cope-hole radius on effective notch stress. Comparison of the results with commonly used design guidance documents reveals that the effective notch stress approach provides a conservative estimate of the fatigue strength of the specimens tested in this experimental programme.
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This paper presents data from fiber-optic strain monitoring of the Nine Wells Bridge, which is a three-span, pretensioned, pre-stressed concrete beam-and-slab bridge located in Cambridgeshire in the United Kingdom. The original deployment... more
This paper presents data from fiber-optic strain monitoring of the Nine Wells Bridge, which is a three-span, pretensioned, pre-stressed concrete beam-and-slab bridge located in Cambridgeshire in the United Kingdom. The original deployment at the site and the challenges associated with collecting distributed strain data using the Brillouin optical time domain reflectometry (BOTDR) technique are described. In particular, construction and deployment issues of fiber robustness and temperature effects are highlighted. The challenges of interpreting the collected data as well as the potential value of information that may be obtained are discussed. Challenges involved with relating measurements to the expected levels of prestress, including the effects due to debonding, creep, and shrinkage, are discussed and analyzed. This paper provides an opportunity to study whether two commonly used models for creep and shrinkage, adequately model data collected in field conditions.
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Rapid unplanned urbanisation is driving increasing rainfall-triggered landslide risk in low-income communities in tropical developing countries. Conventional slope stabilisation techniques are often unaffordable and most... more
Rapid unplanned urbanisation is driving increasing rainfall-triggered landslide risk in low-income communities in tropical developing countries. Conventional slope stabilisation techniques are often unaffordable and most disaster-risk-reduction funding is currently spent post-disaster. However, experience in the Caribbean has changed local engineering practice and World Bank policy, demonstrating that community-based surface water drainage is affordable and effective in mitigating urban landslides. New evidence presented in this paper identifies specific informal construction practices generating further landslide hazards and bioengineering schemes most effective for landslide mitigation. A dynamic hydrology–slope stability model is used to simulate the factor of safety response of nine slope classes (angle and soil strength) to progressive vegetation removal, slope cutting and loading, for six design storms. The effectiveness of 76 bioengineering schemes for improving stability is modelled. Key recommendations are that deforestation should be limited and slope cutting avoided as cutting is most detrimental to stability. Site-specific modelling is needed to identify where deep-rooting, lightweight trees might add stability, whereas grasses are beneficial in all locations.
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Ongoing developments in smart technologies such as wireless sensor networks, micro-electro-mechanical systems (MEMS), computer vision, fibre optics and advanced data interpretation techniques may revolutionise structural health monitoring... more
Ongoing developments in smart technologies such as wireless sensor networks, micro-electro-mechanical systems (MEMS), computer vision, fibre optics and advanced data interpretation techniques may revolutionise structural health monitoring (SHM). Dedicated SHM of bridge assets has the potential to produce valuable data-sets and provide owners and managers with information to aid with key questions such as: current performance, margins of safety, actual loading, stress history and risk of fatigue, extent of deterioration and residual life. However, the parameters measured and value of the data obtained will differ when viewed from the perspectives of different stakeholders such as asset owners, designers, contractors and researchers. In this paper the purposes of monitoring are reviewed. A methodology is proposed to facilitate formal discussions between the key stakeholders before any deployment is specified and to ensure that scarce resources are not wasted in the pursuit of data as opposed to information. This approach can be used to determine if there is a prima facie case for the specification of SHM on a project and assess the potential value of any information that may be obtained. The developed methodology has been trialled with five historical monitoring case studies on bridges with which the authors are familiar.
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This paper begins with an extensive review of the literature covering the development of design rules for geostructural systems, beginning with traditional global safety factors and developing through partial factors for loads and... more
This paper begins with an extensive review of the literature covering the development of design rules for geostructural systems, beginning with traditional global safety factors and developing through partial factors for loads and resistances, and then considering the use of mobilization factors to limit soil strains. The paper then aims to distinguish two possible functions for geotechnical factors: to compensate for the uncertainty regarding soil strength, and to limit soil deformations that could compromise the associated structure before the soil strength can be fully mobilized, whatever it is. At present, design procedures generally conflate and confuse ultimate limit state (ULS) checks and serviceability limit state (SLS) deformation checks. Furthermore, most geotechnical engineers wrongly associate ULS with soil failure rather than with structural failure. The paper addresses this fundamental confusion by advocating mobilizable strength design (MSD), which is based on assumed soil-structure deformation mechanisms rather than soil failure mechanisms. It is argued that designs using MSD can guard against damaging structural deformations, either small deformations giving SLS or large structural deformations that must be regarded as ULS even though the associated soil strength may not yet be fully mobilized. This distinction effectively challenges much of the previous literature on limit state design principles for geotechnical applications, even when probabilistic approaches have been proposed. Nevertheless, the paper is informed by the concepts and techniques of decision making under uncertainty, and the paper concludes by considering whether MSD can also be placed in a reliability framework.
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Some UK cities have seen the successful reintroduction of trams to complement and improve public transport services. This paper investigates the impact a hypothetical tramline would have in Bristol. This study was conducted in light of... more
Some UK cities have seen the successful reintroduction of trams to complement and improve public transport services. This paper investigates the impact a hypothetical tramline would have in Bristol. This study was conducted in light of proposals for a bus rapid transit (BRT) network in Bristol. The literature review undertaken concludes that while BRT systems tend to have lower capital costs, a tram system could also be considered. At near-capacity operation, trams may be more effective in encouraging a modal shift away from travelling by car. Evidence from a preliminary simulation model, which was built to evaluate the demand a hypothetical tramline from the airport to the city centre would attract, suggests that a tram would encourage users to switch to public transport. Suggestions for further work for model refinement coupled with better understanding system impacts of the proposed tram system are included.
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The findings of an extensive literature survey focusing on bridge structural health monitoring (SHM) deployments are presented. Conventional, maturing, and emerging technologies are reviewed as well as deployment considerations for new... more
The findings of an extensive literature survey focusing on bridge structural health monitoring (SHM) deployments are presented. Conventional, maturing, and emerging technologies are reviewed as well as deployment considerations for new SHM endeavors. The lack of published calibration studies (and quantification of uncertainty studies) for new sensors is highlighted as a major concern and area for future research. There are currently very few examples of SHM systems that have clearly provided significant value to the owners of monitored structures. The results of the literature survey are used to propose a categorization system to better assess the potential outcomes of bridge SHM deployments. It is shown that SHM studies can be categorized as one (or a combination) of the following: (1) anomaly detection, (2) sensor deployment studies, (3) model validation, (4) threshold check, and (5) damage detection. The new framework aids engineers specifying monitoring systems to determine what should be measured and why, hence allowing them to better evaluate what value may be delivered to the relevant stakeholders for the monitoring investments.
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The liquid limit is defined as the point at which a clay's behaviour changes from liquid to plastic. This transition is in reality gradual, rather than sudden. The definition of when this transition has been crossed must therefore be... more
The liquid limit is defined as the point at which a clay's behaviour changes from liquid to plastic. This transition is in reality gradual, rather than sudden. The definition of when this transition has been crossed must therefore be determined based on some arbitrary criterion. The percussion cup method of determining liquid limit in the manner suggested by Atterberg and subsequently standardised by Casagrande determines liquid limit as the water content at which 25 standard blows are required to cause closure of a standard groove. In order to speed up the determination of the liquid limit, a single-point method is defined in ASTM D4318, and in many other codes, to interpret liquid limit from groove closure at a different numbers of blows by assuming a relationship between water content and the number of blows required for groove closure. These methods differ considerably between different codes of practice currently in use worldwide. This paper examines the procedures for single-point determination of the liquid limit and offers some fundamental explanations that underpin the applicability of these procedures. This paper demonstrates that the variation in single-point liquid limit procedures suggested by various codes of practice can be attributed to the variability of liquid limit devices, rather than to variation in the soils being tested.
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Recent research has clarified the sequence of ground deformation mechanisms that manifest themselves when excavations are made in soft ground. Furthermore, a new framework to describe the deformability of clays in the working stress range... more
Recent research has clarified the sequence of ground deformation mechanisms that manifest themselves when excavations are made in soft ground. Furthermore, a new framework to describe the deformability of clays in the working stress range has been devised using a large database of previously published soil tests. This paper aims to capitalize on these advances, by analyzing an expanded database of ground movements associated with braced excavations in Shanghai. It is shown that conventional design charts fail to take account either of the characteristics of soil deformability or the relevant deformation mechanisms, and therefore introduce significant scatter. A new method of presentation is found which provides a set of design charts that clarify the influence of soil deformability, wall stiffness, and the geometry of the excavation in relation to the depth of soft ground.
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A database of 641 fall cone tests on 101 soil samples from twelve countries has been analysed to determine the best mathematical relationship linking undrained shear strength with liquidity index. From the database, it is shown that the... more
A database of 641 fall cone tests on 101 soil samples from twelve countries has been analysed to determine the best mathematical relationship linking undrained shear strength with liquidity index. From the database, it is shown that the use of a linear relationship linking liquidity index and the logarithm of undrained shear strength that uses the commonly assumed 100-fold factor increase in strength from liquid to plastic limit
over-predicts the measured data of soil strength. The use of a factor of about 35 for the ratio between the strength at liquid limit and that extrapolated to plastic limit is shown to be more realistic. Logarithmic liquidity index is examined and found to also correlate strongly with the logarithm of undrained shear strength, however it is shown that no great statistical improvement is present compared with the semilogarithmic
formulation. When considering data of individual soils a power law fitting is shown statistically to be the preferred mathematical function.
over-predicts the measured data of soil strength. The use of a factor of about 35 for the ratio between the strength at liquid limit and that extrapolated to plastic limit is shown to be more realistic. Logarithmic liquidity index is examined and found to also correlate strongly with the logarithm of undrained shear strength, however it is shown that no great statistical improvement is present compared with the semilogarithmic
formulation. When considering data of individual soils a power law fitting is shown statistically to be the preferred mathematical function.
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A large database has recently been published that details the development of new empirical expressions for the stiffness reduction with strain of clays and silts. In this note, the same database is used to examine two major considerations... more
A large database has recently been published that details the development of new empirical expressions for the stiffness reduction with strain of clays and silts. In this note, the same database is used to examine two major considerations for engineers using these expressions in numerical analyses: the transformation from secant to tangent stiffness and the effect of stress history.
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There has recently been considerable research published on the applicability of monitoring systems for improving civil infrastructure management decisions. Less research has been published on the challenges in interpreting the collected... more
There has recently been considerable research published on the applicability of monitoring systems for improving civil infrastructure management decisions. Less research has been published on the challenges in interpreting the collected data to provide useful information for engineering decision makers. This paper describes some installed monitoring systems on the Hammersmith Flyover, a major bridge located in central London (United Kingdom). The original goals of the deployments were to evaluate the performance of systems for monitoring pre-stressing tendon wire breaks and to assess the performance of the bearings supporting the bridge piers because visual inspections had indicated evidence of deterioration in both. This paper aims to show that value can be derived from detailed analysis of measurements from a number of different sensors, including acoustic emission monitors, strain, temperature and displacement gauges. Two structural monitoring systems are described, a wired system installed by a commercial contractor on behalf of the client and a research wireless deployment installed by the University of Cambridge. Careful interpretation of the displacement and temperature gauge data enabled bearings that were not functioning as designed to be identified. The acoustic emission monitoring indicated locations at which rapid deterioration was likely to be occurring; however , it was not possible to verify these results using any of the other sensors installed and hence the only method for confirming these results was by visual inspection. Recommendations for future bridge monitoring projects are made in light of the lessons learned from this monitoring case study.
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The main phase of excavation for the basements of the British Library at St Pancras, London, was completed in 1987. The project included basements extending up to 25 m deep, through the London Clay and into the Lambeth Group. The... more
The main phase of excavation for the basements of the British Library at St Pancras, London, was completed in 1987. The project included basements extending up to 25 m deep, through the London Clay and into the Lambeth Group. The excavations were formed using both the top-down method and open excavation with ground anchors. Existing major buildings lie within 25 m of the site and London Underground tunnels lie below and adjacent to the site. The purpose of this paper is to present the results of displacement monitoring; they are summarised in the paper and presented in more detail in online supplementary data files. The retaining walls advanced towards the site by up to about 32 mm and the clays expanded rapidly on unloading beneath the excavations, causing the Victoria Line tunnels to heave by up to 22 mm. The slow progress of the project provided an unusual opportunity to monitor ground and structure movements in the surroundings before site activity began. Ironically, it was found that the largest settlements of adjacent buildings were caused by the installation of equipment intended to measure the settlements. Extensive condition surveys were carried out, but no damage to adjacent structures or tunnels has been recorded.
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The findings of an extensive literature review on the permeability of hot-mix asphalt concrete are detailed in a state-of-the-art report on the measurement and interpretation of asphalt concrete permeability data. The permeability of... more
The findings of an extensive literature review on the permeability of hot-mix asphalt concrete are detailed in a state-of-the-art report on the measurement and interpretation of asphalt concrete permeability data. The permeability of asphalt concrete is affected by a range of factors with various levels of importance, which are reviewed along with their impact on the coefficient of permeability. Many theoretical, empirical, semiempirical, and numerical models have been developed to predict permeability, using a range of indicators. Some of these models are reviewed and their advantages and shortcomings discussed. Recent advances in X-ray tomography studies are also summarized. The review reveals that field permeability measurements are not reported to match numerically well with laboratory measurements, though there is some correlation. The reviewed test methods for permeability all rely on an assumption of laminar flow that is unlikely in more porous mixtures. Attempts to measure connected air voids improve the chances of obtaining more meaningful correlations between permeability and air voids, regardless of the mathematical model used to link the two quantities. The lift-thickness to nominal maximum aggregate size (NMAS) ratio and/or changes in the binder content has a less significant effect on permeability than changes in the porosity and/or mix gradation. Air void gradients and distributions in compacted asphalt concrete mixtures can now be assessed with X-ray techniques: the distribution of air voids appears to be nonuniform in laboratory-prepared specimens.
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An analysis is presented of a database of 67 tests on 21 clays and silts of undrained shear stress-strain data of fine-grained soils. Normalizations of secant G in terms of initial mean effective stress p' (i.e., G/p' versus log gamma) or... more
An analysis is presented of a database of 67 tests on 21 clays and silts of undrained shear stress-strain data of fine-grained soils. Normalizations of secant G in terms of initial mean effective stress p' (i.e., G/p' versus log gamma) or undrained shear strength c(u) (i.e., G/c(u) versus log gamma) are shown to be much less successful in reducing the scatter between different clays than the approach that uses the maximum shear modulus, G(max), a technique still not universally adopted by geotechnical researchers and constitutive modelers. Analysis of semiempirical expressions for G(max) is presented and a simple expression that uses only a void-ratio function and a confining-stress function is proposed. This is shown to be superior to a Hardin-style equation, and the void ratio function is demonstrated as an alternative to an overconsolidation ratio (OCR) function. To derive correlations that offer reliable estimates of secant stiffness at any required magnitude of working strain, secant shear modulus G is normalized with respect to its small-strain value G(max), and shear strain gamma is normalized with respect to a reference strain gamma(ref) at which this stiffness has halved. The data are corrected to two standard strain rates to reduce the discrepancy between data obtained from static and cyclic testing. The reference strain gamma(ref) is approximated as a function of the plasticity index. A unique normalized shear modulus reduction curve in the shape of a modified hyperbola is fitted to all the available data up to shear strains of the order of 1%. As a result, good estimates can be made of the modulus reduction G/G(max) +/- 30% across all strain levels in approximately 90% of the cases studied. New design charts are proposed to update the commonly used design curves.
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Rainfall-triggered landslides are increasingly a concern in rapidly urbanising areas around the globe. Assessing the stability of slopes is important for geotechnical engineers and planners working in these regions. Saturated hydraulic... more
Rainfall-triggered landslides are increasingly a concern in rapidly urbanising areas around the globe. Assessing the stability of slopes is important for geotechnical engineers and planners working in these regions. Saturated hydraulic conductivity is key parameter for assessing the hydrological drivers of slope instability. This paper presents a recent citizen-science case study in Quito, Ecuador, in which saturated hydraulic conductivity measurements were taken in the field on a fine-grained volcanic sediment, often referred to as cangahua, were obtained as part of the Tomorrow's Cities project on urban multi-hazards and disaster risk management. These data are then used along with a recent soil database of Quito soils (Quito/GEO-299) and other locally obtained soil data and the Combined Hydrology And Stability Model (CHASM) to assess the stability of slopes in a hillside community in South Quito. The paper focuses on the variability of key slope stability parameters, including saturated hydraulic conductivity to assess the plausible ranges of behaviour for slopes in this area.
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A-priori estimates of maximum scour depth are important for bridge engineers, managers and owners. HEC-18 is an established method which uses empirical equations to estimate bridge scour. This paper applies the HEC-18 methodology to... more
A-priori estimates of maximum scour depth are important for bridge engineers, managers and owners. HEC-18 is an established method which uses empirical equations to estimate bridge scour. This paper applies the HEC-18 methodology to compute maximum scour depth for 936 bridge piers for which field scour depth measurements are available from an online database from the United States Geological Survey (USGS). The results are in general agreement with past research efforts which suggest that the HEC-18 methodology tends to overestimate maximum bridge pier scour depth. The database is also categorized into various sub-sets to study the effect of different particle sizes and devices used to measure scour in the field.
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Hydraulic filling is used for land reclamation work and/or to increase the ground level of low-lying areas. Changes in gradation properties of the hydraulic fill is to be expected during hydraulic filling process which comprises dredging,... more
Hydraulic filling is used for land reclamation work and/or to increase the ground level of low-lying areas. Changes in gradation properties of the hydraulic fill is to be expected during hydraulic filling process which comprises dredging, transportation, deposition, and compaction. These changes in gradation can influence the hydraulic conductivity (permeability coefficient) of the resulting hydraulic fill mass. This hydraulic conductivity is further exacerbated by potential ponding of the transient remnant sea water within the constructed fill mass and its extent in relation to location of points of discharge and the groundwater regime of the area. This paper examines the effect of change in gradation on the hydraulic fill mass coefficient of permeability, using the grading entropy framework to investigate changes in the coefficient of permeability of the hydraulic fill mass. The paper also examines the possibility of applying the gradation entropy framework to assess the liquefaction potential of sand fill mixtures 'after deposition' and the in-situ granular foundation strata due to seismic events.
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The SAFER project had the aim of developing improved tools and enhanced datasets for seismic hazard assessment in Nepal. The project developed a geotechnical database for the Kathmandu valley (SAFER/GEO-591). During the project additional... more
The SAFER project had the aim of developing improved tools and enhanced datasets for seismic hazard assessment in Nepal. The project developed a geotechnical database for the Kathmandu valley (SAFER/GEO-591). During the project additional geotechnical site investigation data was collected including standard penetration testing and new borehole logging. Significantly, new Cone Penetration Testing (CPT) was carried out. This paper presents some further analysis of the collected CPT data and compares the test results against previously published analysis frameworks. The use of CPT data to estimate soil shear wave velocity in the Kathmandu valley along with normalisation procedures to account for the effects of stress level is discussed. Use of the new CPT data along with established soil classification charts is also presented in this paper.
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To investigate the variation of undrained shear strength with changes in water content, determination of a value of undrained shear strength at the liquid limit is needed. There is debate as to the extent of the typical range of values of... more
To investigate the variation of undrained shear strength with changes in water content, determination of a value of undrained shear strength at the liquid limit is needed. There is debate as to the extent of the typical range of values of undrained shear strength at the liquid limit. In this paper, the undrained shear strength is measured using the miniature laboratory shear vane apparatus and compared with values back-analysed from British Standard fall-cone test data. Four geomaterials: Kaolin, Bentonite, Chalk and Bothkennar clay were selected for testing. The variation of the undrained shear strength values from both testing approaches with changing water content was also studied and compared with the results of previous work. The paper reports a narrow range of undrained shear strength values at the liquid limit for the geomaterials tested.
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An approach for assessing the value of a structural health monitoring (SHM) system for a bridge prior to deployment has been developed. The methodology systematically obtains the views of three key stakeholders in bridge SHM management:... more
An approach for assessing the value of a structural health monitoring (SHM) system for a bridge prior to deployment has been developed. The methodology systematically obtains the views of three key stakeholders in bridge SHM management: the asset owner, the structural engineer and the SHM engineer. The output of the methodology is a numerical value that indicates the approximate likelihood of a SHM system generating value for an asset owner. This paper applies this framework to two structures which span the River Thames in Central London, UK. The first structure is a 434 m long concrete, two-way road and footbridge, with a superstructure primarily comprising a concrete deck and two reinforced concrete box girders. In 2017, the bridge was the subject of a year-long monitoring programme which collected thermal and movement data to help refine structural models and inform maintenance repairs. The second structure consists of a pair of cable-stayed footbridges which are built on either side of an existing rail bridge. Each bridge deck is 300 m in length and is suspended from steel rods known as deck stays, made up of over 4 km of cable. Initially, there were no prior notions about what system should be implemented, but after discussions with the asset owner, a system to monitor the tension in the cables is considered. From the resulting discussions, the retrospective application of the framework resulted in a value-rating (VR) of 3.8, whilst the second structure received a rating of 3.4. A detailed discussion on value monitoring from industry experts is presented.
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Bridges are important infrastructure assets that are vital for the connectivity of communities. Visual inspections remain a key method for bridge condition monitoring. However, visual inspections are often considered to be highly... more
Bridges are important infrastructure assets that are vital for the connectivity of communities. Visual inspections remain a key method for bridge condition monitoring. However, visual inspections are often considered to be highly subjective and therefore alternative technologies are often proposed as a means of replacing or enhancing current visual inspection practices. This paper presents the results of a survey which aims to document the emerging trends for future visual inspection practice related to bridges. The implementation of new technological solutions has the potential to improve the quality of inspection data, reduce the safety risks posed to visual inspectors by moving more of the process off-site and improve the quantification of the rate of change in condition. The survey covers two key topics: (i) Emerging data capture methods and (ii) Emerging data analysis methods. Emerging data capture methods include: use of uncrewed vehicles, 360°cameras, photogrammetry, laser scanners, point cloud systems, and Interferometric Synthetic Aperture Radar (InSar). Emerging data analysis methods include: remote inspection, augmented reality and virtual reality, digital image correlation, artificial intelligence, Big Data and the Internet of Things. The survey concludes with a detailed discussion on the opportunities and barriers to implementation of the reviewed technologies and approaches.
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Bridge scour is a major cause of bridge collapse worldwide. Various approaches are available to estimate levels of scouring due to hydraulic loading. Such scour depth assessment methodologies typically employ a series of empirical and... more
Bridge scour is a major cause of bridge collapse worldwide. Various approaches are available to estimate levels of scouring due to hydraulic loading. Such scour depth assessment methodologies typically employ a series of empirical and semi-empirical equations to estimate scour around a bridge element. This work examines three such methodologies, namely the Hydraulic Engineering Circular Number 18 method (HEC-18) 4 th edition, the HEC-18 5 th edition method and the Texas A&M University method (TAMU). The paper compares the results from these three calculation methods with field data from 23 bridge piers (eight bridges) located in the State of Maine (USA). The paper investigates the levels of conservatism in the estimates of scour depth calculated using these three methodologies. All three approaches tend to give conservative estimates of maximum scour depth, especially for low values of scour depth, when compared to the field dataset examined in this paper.
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Geotechnical databases are useful for providing quantitative assessments of the variability of important geotechnical properties. Such databases are vital for the development and calibration of transformation models which can be used to... more
Geotechnical databases are useful for providing quantitative assessments of the variability of important geotechnical properties. Such databases are vital for the development and calibration of transformation models which can be used to estimate more complex variables from more fundamental parameters. This study examines two recently compiled databases of hydraulic conductivity of materials important to road construction, namely FG/KSAT-1358 for fine-grained soils, and AC/k-1624 for asphalt concrete mixtures. The influence of statistically classified outliers on the regression coefficients in recently published transformation models derived from these two databases is studied. It is shown that the regression coefficients from the transformation model produced using AC/k-1624 are more influenced by the outlier removal process compared with those from FG/KSAT-1358. The Akaike Information Criterion is used to evaluate the best fit probability density functions to the key database parameters. It is shown that the 'loglogistic' distribution is the best pdf to describe the variation of key parameters from both databases while the 'lognormal' distribution describes best the variation of the void ratio (e) data in FG/KSAT-1358.
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Piled foundations generally fail due to excessive settlements causing damage to the supported structure. While various methods are available to predict pile settlements, historically codes of practice have relied upon large factors of... more
Piled foundations generally fail due to excessive settlements causing damage to the supported structure. While various methods are available to predict pile settlements, historically codes of practice have relied upon large factors of safety to ensure pile plunging is sufficiently unlikely. This can lead to confusion between serviceability and collapse limit states as both are concerned with limiting settlements. Modern codes of practice do require the serviceability limit state to be considered independently. However, guidance is rarely provided as to the specific method of predicting settlement and in some cases the expressed expectation is that this condition is satisfied for a pile designed according to the collapse limit state. Therefore, quantifying the settlement reduction provided by a design code is of interest to the engineer as this allows the level of design conservatism to be evaluated. However, this can only be done with a sufficiently large database of pile load tests in the soil deposit of interest. In this paper, two design codes are applied to a dataset of pile tests in London clay. Measured settlements are then obtained from load-test results and compared with those obtained from an unfactored ‘α-method’ analysis to obtain the settlement reduction provided by the design code.
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Quito, Ecuador, is a city at risk of many hazards including earthquakes, volcanic eruptions and landslides, compounded by the widespread presence of problematic volcanic soils known as Cangahua. This paper presents the preliminary results... more
Quito, Ecuador, is a city at risk of many hazards including earthquakes, volcanic eruptions and landslides, compounded by the widespread presence of problematic volcanic soils known as Cangahua. This paper presents the preliminary results of data analyses undertaken on a new geotechnical database for Quito, compiled from a variety of sources. It is envisaged that this database will be utilised primarily for improving our understanding of landslide hazard drivers in communities in and around the city. The preliminary statistical analyses include probability density functions and regression models for soil parameters. A difference in geotechnical variability between the north and the south of the city was observed. The study also presents data from unmanned aerial vehicle (UAV) mapping of an informally constructed hillside community in Quito, identifying house-scale slope features (e.g. cut slopes and house loading) that may affect local landslide hazard processes. Together, the statistical analyses of these datasets will provide the inputs for physics-based stochastic slope stability modelling. Recommendations for future data collection are given to support the development of a higher resolution Quito database and facilitate the improvement of community-scale slope stability assessments.
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The 2015 Gorkha earthquake caused considerable infrastructure damage and disruption. In the years that followed, the need emerged for planners to access hazard maps and better plan future developments and upgrades to existing... more
The 2015 Gorkha earthquake caused considerable infrastructure damage and disruption. In the years that followed, the need emerged for planners to access hazard maps and better plan future developments and upgrades to existing infrastructure assets. In light of this, the ability to run stochastic simulations is important for scenario planning. When modelling geotechnical phenomena soil variability needs to be assessed. For stochastic modelling efforts, soil variability should be assessed statistically. There are two key geological units in the Kathmandu valley: the Gokarna and Kalimati formations. These valley sediments are highly variable but high-quality geotechnical data is scarce. To mitigate this data scarcity, a recently developed geotechnical database called SAFER/GEO-591 is used to determine the best fit probability density functions for key soil parameters in each formation relevant for geotechnical design and modelling efforts. The best-fit probability density functions can be used in modelling liquefaction potential, site, and foundation response for new and existing constructions in the valley.
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The Mobilisable Strength Design (MSD) philosophy has been used in various applications related to underground construction, e.g. for analysis of deep foundation and retaining wall performance. MSD requires simple models for the... more
The Mobilisable Strength Design (MSD) philosophy has been used in various applications related to underground construction, e.g. for analysis of deep foundation and retaining wall performance. MSD requires simple models for the stress-strain behaviour of soils. The use of a mobilisation factor on undrained strength to limit soil mobilisation was introduced in BS8002 in 1994. To assist with MSD calculations, the mobilisation strain framework (MSF) has been developed to allow geotechnical engineers to account for the non-linear behaviour of fine-grained soils in routine geotechnical design. In this paper, triaxial and pressuremeter test data from the London Clay deposit are analysed, using the MSF, to study the effects of anisotropy on both the mobilisation strains and non-linearity exponent. The implications for design of underground constructions are also discussed.
Research Interests:
The feasibility of a tunnel, foundation or excavation project is to some extent dependent on limiting the potential ground movements during construction. To make such an assessment it is important to quantify the stress-path dependent... more
The feasibility of a tunnel, foundation or excavation project is to some extent dependent on limiting the potential ground movements during construction. To make such an assessment it is important to quantify the stress-path dependent behaviour of the soil undergoing undrained lateral and vertical stress relief. At an early stage in the project, site-specific test data is limited and so predictions must necessarily be based upon expected characteristics of the soil deposit. Analysis of a recently compiled database RFG/TXCU-278 has demonstrated a method of quantifying the variability of stress-strain data from stress-path tests that are more frequently encountered in commercial practice (consolidated-undrained triaxial compression and extension tests) for use in design sensitivity analyses. A soil non-linearity parameter (b) is investigated using the database RFG/TXCU-278 and a series of previously reported tests performed on intact Bothkennar Clay. Evidence from both databases suggests that the variability of b is not strongly linked to the effects of shear mode, OCR, strain rate, or plasticity. It is shown that reasonable predictions of nonlinear behaviour up to a load factor (σmob/σfailure) of 0.8 can be achieved using the MSD-MSF method for a rigid pad test.
Research Interests:
Bridge engineers specifying, designing and installing Structural Health Monitoring (SHM) systems need to be able to provide reliable information over the very long design lives expected of critical infrastructure assets such as bridges.... more
Bridge engineers specifying, designing and installing Structural Health Monitoring (SHM) systems need to be able to provide reliable information over the very long design lives expected of critical infrastructure assets such as bridges. It is essential that asset managers can have confidence that any significant anomalies or changes in the performance of the structure will be detected. The resources and planning needed to keep such systems functioning is rarely reported as many research deployments are of short duration. In 2007 a wireless sensor network was installed in the Hessle Anchorage chambers of the Humber Bridge in the United Kingdom to monitor parameters that could affect the durability of the main suspension cables of the bridge. This deployment was part of a wider project aimed at examining the potential for using wireless network systems to monitor infrastructure assets. The initial planned duration of the project was six months. It has however now been in place and operational for over ten years. This paper discusses the maintenance undertaken, modifications required, and long-term performance of this installation along with the significance of the long-term data set that has been collected.
Research Interests:
Prediction of pile performance often relies upon full-scale pile load testing to better manage geotechnical uncertainty and enable less conservative design. Many analysis methods (e.g. the α-method) require a load test database for... more
Prediction of pile performance often relies upon full-scale pile load testing to better manage geotechnical uncertainty and enable less conservative design. Many analysis methods (e.g. the α-method) require a load test database for calibration. Databases of these tests can provide detailed design guidance in specific geological deposits. However, full scale tests are expensive, and the results, for a variety of reasons, are not always shared with the wider geotechnical community. The DINGO database is an openly accessible database of full-scale pile load tests carried out in UK soils. This paper reports on the building of the database as well as the challenges involved and lessons learnt in collecting and sharing the pile test data. The pile test data in the database is presented by sorting for ‘Geological Deposit’, ‘Construction Decade’ and ‘Construction Type’. A preliminary classification of the quality of information contained in the database is also presented.
Research Interests:
The Seismic Safety and Resilience of Schools in Nepal (SAFER) project has an important aim of producing improved tools for geotechnical and earthquake engineers to assess seismic hazard in the Kathmandu Valley, Nepal. Geo-databases have... more
The Seismic Safety and Resilience of Schools in Nepal (SAFER) project has an important aim of producing improved tools for geotechnical and earthquake engineers to assess seismic hazard in the Kathmandu Valley, Nepal. Geo-databases have the potential to offer geotechnical practitioners means to improve a-priori predictions of important soil parameters in geotechnical design. In this paper, some recent work to develop a new database of geotechnical information (SAFER/GEO-591) including shear wave velocity measurements is reported. Attempts to develop new transformation models to better predict shear wave velocity from more basic parameters such as SPT-N values are presented. Use of kriging to better map shear wave velocity for the study area is recommended as a suitable alternative to the presented correlations.
Research Interests:
Rainfall-triggered landslides are an ‘everyday risk’ to Small Island States, such as Saint Lucia in the Caribbean, and have the potential to destroy or damage buildings and disrupt lifelines such as roads and pipelines. To better evaluate... more
Rainfall-triggered landslides are an ‘everyday risk’ to Small Island States, such as Saint Lucia in the Caribbean, and have the potential to destroy or damage buildings and disrupt lifelines such as roads and pipelines. To better evaluate these landslide hazards, efforts have been made to develop decision-support tools linking rainfall scenarios to stability for different types of road cut slope. Many thousands of stochastic simulations can be performed using a combined hydrology and slope stability model (CHASM) which requires inputs of slope cross-sectional geometry, soil and hydrological parameters which allows representative rainfall-triggered landslide scenarios to be produced. To use CHASM for this purpose the statistical variation of the relevant geotechnical properties such as friction angle needs to be assessed. This paper presents the analysis of an updated database for Saint Lucian soils that has been compiled using data supplied by the Government of Saint Lucia Ministry of Infrastructure, Port Services and Transport. The Coefficient of Variation values of the key soil mechanics parameters are reported and previously developed transformation models for estimating effective friction angle are updated. The Weibull statistical distribution is shown to be the best fit to the friction angle data.
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Rainfall-triggered landslides are increasing in the humid tropics, and Small Island Developing States are disproportionately affected. Frequent shallow slides in hillside cuttings along roads and in communities hinder sustainable... more
Rainfall-triggered landslides are increasing in the humid tropics, and Small Island Developing States are disproportionately affected. Frequent shallow slides in hillside cuttings along roads and in communities hinder sustainable development. Larger, less frequent storms cause hundreds of landslides that block lifeline roads, impede disaster response and reverse economic growth. Top-down Disaster Risk Reduction (DRR) policies and approaches aiming to transfer conventional landslide assessment science and engineering practices are not always suitable in these data- and resource-limited contexts. This paper recognises the emergence of co-production approaches as part of the resilience paradigm response to DRR science-policy-practice gaps. We present a case study from Saint Lucia, Eastern Caribbean, in which government engineers and policymakers have partnered with the authors to co-produce landslide hazard assessment data and prototype decision support tools to strengthen landslide hazard management along lifeline roads.
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This paper presents a sensitivity study of simulation-based Probabilistic Seismic Hazard Analysis (PSHA) for Kathmandu, Nepal. Two aspects are investigated in detail: (i) the technique for simulating fault ruptures compatible with scaling... more
This paper presents a sensitivity study of simulation-based Probabilistic Seismic Hazard Analysis (PSHA) for Kathmandu, Nepal. Two aspects are investigated in detail: (i) the technique for simulating fault ruptures compatible with scaling laws and fitting into the Main Himalayan Trust (MHT) and (ii) the choice of different Ground Motion Prediction Equations (GMPEs). Since the 2015 Gorkha earthquake, a number of new studies have provided new approaches to model the MHT as a single seismic source. This more realistic characterization of the MHT has resulted in higher peak ground acceleration (PGA) for all of Nepal and in particular for the Kathmandu Valley. Here, the results of a new simulation-based code are compared with those by the software OpenQuake. It is specifically assessed how different source simulation methods influence the hazard calculations. Furthermore, the influence of different GMPEs assumed for subduction earthquakes is assessed for the specific case of Kathmandu, which is only 11 km above the MHT. Results show that because of the proximity to the megathrust, the estimated hazard is very sensitive to different choices. The results of this study may be useful for informing ongoing efforts in Nepal to update the building code with a new seismic hazard map. Understanding the sensitivity and robustness of PSHA is critical from a policy and preparedness perspective.
Research Interests:
Modelling soil nonlinearity in pile settlement analysis often requires numerical analysis based either on 1-dimensional "t-z" curves or even multi-dimensional constitutive models, which may not be appealing to geotechnical engineers. A... more
Modelling soil nonlinearity in pile settlement analysis often requires numerical analysis based either on 1-dimensional "t-z" curves or even multi-dimensional constitutive models, which may not be appealing to geotechnical engineers. A number of alternative approaches are available that take advantage of simplified constitutive models and analytical methods to develop solutions that are suitable for spreadsheet calculations. This paper investigates the error introduced by the assumptions in two such models. A theoretical "t-z" curve is developed based on a simplified constitutive model and a new approximate approach developed that incorporates nonlinearity for both shaft and base resistance. This is compared to the predictions of a linear elastic-perfectly plastic method using an informed choice of linear elastic stiffness. A basic sensitivity study is carried out comparing the two approaches with a 1-dimensional numerical solution.
Research Interests:
When designing ground investigations there is usually a requirement to fill large gaps in existing knowledge. In the developing world, specifically in seismic prone areas, this systematic lack of information affects the ability for... more
When designing ground investigations there is usually a requirement to fill large gaps in existing knowledge. In the developing world, specifically in seismic prone areas, this systematic lack of information affects the ability for practitioners to assess seismic risk. This paper presents the rationale and results of a ground investigation undertaken in Central Nepal to inform seismic hazard assessment, as part of the EPSRC funded project Seismic Safety and Resilience of Schools in Nepal (SAFER). Geological information and geotechnical parameters are presented. Downhole methodology has been used to derive an in situ shear wave velocity profile for seismic response analysis in a region which is currently reliant on seismic shear wave velocity correlations. This research presents discussion and comparison of velocity profiles obtained at other locations in the Kath-mandu Valley and introduces new information on the basin topography.
Research Interests:
Residential damp can be detected by measuring the temperature and relative humidity in a given space. With these values, one can infer the dew point, which is an accurate indicator for condensation. By installing sensor networks that can... more
Residential damp can be detected by measuring the temperature and relative humidity in a given space. With these values, one can infer the dew point, which is an accurate indicator for condensation. By installing sensor networks that can take these relevant measurements, urban sensing systems could be created that help tackle the problem of residential damp. This paper centres in on this concept. Potential urban sensing solutions relevant to damp are surveyed. Three existing initiatives were found as well as a variety of potential solutions, demonstrating the feasibility of such a network to be installed. A sensor-known as the 'Frogbox'-developed from an existing initiative is then deployed in a student residence over a two-week period. From the deployment, it was found that the average humidity was at 56%, which is above the recommended amount. Improvements to the Frogbox could be made by adding a real-time visualisation feature. Given findings from the review and case study, a conceptual urban sensing model for a university student population is then developed.
Research Interests:
Reliable probabilistic seismic hazard analysis (PSHA) for Nepal is a long-term goal that different researchers have been working on in the last decade. Especially after the 2015 Gorkha earthquake, several classical probabilistic seismic... more
Reliable probabilistic seismic hazard analysis (PSHA) for Nepal is a long-term goal that different researchers have been working on in the last decade. Especially after the 2015 Gorkha earthquake, several classical probabilistic seismic hazard analysis studies have been carried out for the entire Nepal. Herein, an alternative simulation-based PSHA is performed for the Kathmandu basin generating a stochastic catalogue of events using information about seismogenic zones from recent research studies. Different ground motion prediction equations have been adopted. Results show the necessity for a ground motion prediction model that is tailored for Nepal.
Research Interests:
The SAFER (Seismic Safety and Resilience of Schools in Nepal) project work package "New generation seismic hazard for Nepal" aims to produce relevant outcomes for earthquake engineers working in Nepal. In order to improve disaster risk... more
The SAFER (Seismic Safety and Resilience of Schools in Nepal) project work package "New generation seismic hazard for Nepal" aims to produce relevant outcomes for earthquake engineers working in Nepal. In order to improve disaster risk management, enhanced seismic hazard assessment is needed. Previous studies show there is insufficient geotechnical data in Kathmandu Valley to prepare a realistic hazard map. The SAFER project aims in part to collect and obtain new geotechnical data to assist with this aim. This paper presents data from a recent seismic microtremor test undertaken in the Kathmandu Valley.
Research Interests:
Prediction of ground movements requires a reliable estimation of soil representative stress-strain behaviour. To do this an assessment of in-situ (‘preshear’) conditions and the associated influence on the average mobilised soil strength... more
Prediction of ground movements requires a reliable estimation of soil representative stress-strain behaviour. To do this an assessment of in-situ (‘preshear’) conditions and the associated influence on the average mobilised soil strength and strain is needed. While many studies focus on undrained shear strength, less effort has been reported for soil shear strain in the context of foundation design. The influence of different experimental and prediction techniques to determine representative soil shear stress-strain design parameters is worthy of study. In this paper, new experimental data is presented from a series of triaxial and oedometer tests on kaolin. The results demonstrate increasing values of normalised undrained shear strength and reference shear strain with increasing OCR.
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Visual inspection is the most common form of condition monitoring used by bridge owners. Information derived from visual inspection data is commonly used to indicate the performance of bridge stocks and inform bridge management decisions.... more
Visual inspection is the most common form of condition monitoring used by bridge owners. Information derived from visual inspection data is commonly used to indicate the performance of bridge stocks and inform bridge management decisions. However, several studies have highlighted that the inherently subjective nature of the methods used to record this data can result in uncertainty, due to differences between different inspectors' perceptions of the severity and extent of defects. It is important for asset managers to understand the nature of this uncertainty and the implications for decision making. This paper reports the results of a study which compared scoring of bridge defects by pairs of independent inspectors across 200 bridge structures on England's strategic road network. A sample of 200 structures was selected to be representative of Highways England's stock with regard to, inter alia, age, condition and structural form. Routine Principal Inspections for these sample structures, undertaken every six years by the relevant maintaining agents, were also attended by inspectors from WSP Ltd, with defects scored independently by each inspector. The results of these comparisons were used to derive an empirical profile of the uncertainty in different individual defect severity and extent scores. Statistical methods were then used to derive empirical probability density functions for the values of bridge and stock level condition metrics according to the widely adopted Bridge Condition Indicator system. The reported results highlight trends in the reliability of individual defect scores and the impact of uncertainty on commonly used performance metrics.
Research Interests:
Footings subjected to dynamic loads are commonly designed under the simplifying assumption of linear or equivalent-linear soil behaviour. Even though this approach is simple to implement and, in some cases, could take advantage of... more
Footings subjected to dynamic loads are commonly designed under the simplifying assumption of linear or equivalent-linear soil behaviour. Even though this approach is simple to implement and, in some cases, could take advantage of available closed-form solutions, the outcomes remain a gross approximation. Although considerable research has been conducted for the case of high-amplitude footing vibrations, where uplift, slippage or even failure may occur, there remains a research gap for small to medium strain amplitudes, for which the behaviour is also non-linear. To address this problem, a numerical methodology is developed herein, for the analysis and design of shallow footings, while taking into consideration shear modulus degradation and hysteretic damping increase effects for the foundation subsoil. The analysis methodology is based on the implementation of the modified hyperbolic model as a user-defined formulation into the explicit finite difference code FLAC. Focus is then given on a rigid strip surface foundation subjected to a harmonic rocking motion, and results from preliminary analyses are presented in terms of the variation of the dynamic impedance with the dimensionless frequency of the excitation. Different excitation amplitudes are examined to demonstrate the effects of soil non-linearity, while strain rate effects are also investigated.
Geotechnical and geological data are needed for the seismic hazard assessments that inform earthquake risk management and resilient engineering design. This paper reviews information typical of that available in developing countries for... more
Geotechnical and geological data are needed for the seismic hazard assessments that inform earthquake risk management and resilient engineering design. This paper reviews information typical of that available in developing countries for the definition of the shear wave velocity in the first 30 meters of soil (VS30). This paper aims to determine optimal resolutions for different data sources in relation to the definition of VS30 maps and the identification of an optimal strategy for localisation of new site investigations (i.e., new boreholes). The context of developing countries, being characterised by endemic lack of high-quality archived data and lack of systematic financial sources, makes the scope of the study challenging and different from the geological and geotechnical approaches typically used in developed countries. Within this context, the auxiliary employment of empirical correlations for the evaluation of VS30 is also discussed as a means of defining cost-effective investigation strategies for developing countries. The Kathmandu Basin in Nepal is used as a representative case study. Preliminary data collected within the University of Bristol led project SAFER-Seismic Safety and Resilience of Schools in Nepal-are critically analysed to the aim of identifying (i) the critical resolution for geodatabase layers (e.g., the digital elevation model) and (ii) the best location for new borehole tests aimed at improving the quality of the VS30 model for the Basin. The approach outlined for Nepal is applicable to other seismic prone areas in the developing world.
Research Interests:
Pavements are ubiquitous civil engineering structures which form the important lifelines that connect communities. They must remain serviceable after events such as flooding, cyclones and extreme freeze-thaw cycles. The hydraulic... more
Pavements are ubiquitous civil engineering structures which form the important lifelines that connect communities. They must remain serviceable after events such as flooding, cyclones and extreme freeze-thaw cycles. The hydraulic conductivity of road pavements is important to understand their performance. This paper summarises some recent work aimed at improving the prediction of the hydraulic conductivity of asphalt concrete. Laboratory test results show the use of the ‘hand pumping method’ to measure the percentage of connected air voids in asphalt concrete specimens. The representative pore size concept is used to analyse an updated database of hydraulic conductivity measurements of asphalt concrete. The effect of nominal maximum aggregate size is studied. Preliminary efforts to use the grading entropy framework to predict the hydraulic
conductivity of asphalt concrete are reported.
conductivity of asphalt concrete are reported.
Research Interests:
For assessment of slope stability in data-scarce regions prone to natural hazards, modelling relies, to a large degree, on estimates of the effective friction angle. Using a database, comprising soil data from Saint Lucia in the Eastern... more
For assessment of slope stability in data-scarce regions prone to natural hazards, modelling relies, to a large degree, on estimates of the effective friction angle. Using a database, comprising soil data from Saint Lucia in the Eastern Caribbean, both simple regression and multiple linear regression analysis were performed. These analyses correlate various basic soil parameters with the effective friction angle measurements contained in the database. The developed statistical relationships are then employed for the estimation of the effective friction angle for use in a slope stability simulation scenario. These analyses show the narrowing of the expected range of results for the slope factor of safety when more soil parameters are used in the estimation of effective friction angle.
Research Interests:
Geotechnical designers and modellers must capture and quantify the variability of key soil properties to make engineering decisions. There is a long history in geotechnical engineering of assembling large databases of past soil tests.... more
Geotechnical designers and modellers must capture and quantify the variability of key soil properties to make engineering decisions. There is a long history in geotechnical engineering of assembling large databases of past soil tests. This paper shows the use of geotechnical databases in two contexts: (a) slope stability modelling in the Eastern Caribbean and (b) settlement response of bored piles in London Clay.
Research Interests:
Landslide risk is increasing in tropical developing countries as rapid informal construction increases the susceptibility of slopes to rainfall-triggered landslides. These ‘everyday hazards’ adversely affect the livelihoods of hillside... more
Landslide risk is increasing in tropical developing countries as rapid informal construction increases the susceptibility of slopes to rainfall-triggered landslides. These ‘everyday hazards’ adversely affect the livelihoods of hillside communities, hinder sustainable development, indicate a systemic lack of resilience and can be linked to the stagnation of a country’s economic growth. A physically-based model of dynamic rainfall infiltration and slope hydrology coupled with limit equilibrium analysis is used to identify the progressive effects of urbanisation on slope stability over time, and the sensitivity of such analyses to variations in mechanical and hydraulic soil properties. The greatest reductions in stability are associated with slope cutting; however, planting grasses and, in some cases light-weight trees, can improve stability. For the majority of deforested slopes without cuts, mechanical soil properties have the strongest influence on stability; however, for slopes close to the point of failure, variations in saturated hydraulic conductivity become more significant.
Research Interests:
Hydraulic conductivity is an important material parameter for pavement engineers. The ability to make a priori estimates of the coefficient of permeability of road pavement materials is very useful when studying issues of pavement... more
Hydraulic conductivity is an important material parameter for pavement engineers. The ability to make a priori estimates of the coefficient of permeability of road pavement materials is very useful when studying issues of pavement durability and predicting pavement performance. This paper presents two laboratory databases assembled from data sourced from the literature. Using a database of permeability tests on fine-grained soils, the ability of the Kozeny-Carman void ratio function to interpret the data is examined alongside a simple power-law relationship. A second database of permeability measurements on asphalt concrete specimens is used to re-examine the ‘representative pore size’ concept as a method of predicting the coefficient of permeability. The influence of Nominal Maximum Aggregate Size (NMAS) on the coefficient of permeability is also studied.
Research Interests:
The organisations responsible for managing bridge assets in the United Kingdom collect large quantities of data on their bridges. A primary aspiration in the collection of asset data is that it can be processed into useful information... more
The organisations responsible for managing bridge assets in the United Kingdom collect large quantities of data on their bridges. A primary aspiration in the collection of asset data is that it can be processed into useful information that can inform decisions about future management of structures and enhance industry best practice. To enable this, bridge managers must take care to specify appropriate parameters to be recorded, in conjunction with a practical recording interval. In addition, the design of data collection and recording processes is key to ensuring that the data obtained can be transformed into useable information. This study draws on perspectives from a series of interviews with key agents involved in the management of bridges in the United Kingdom. The paper explores the nature of the data that is collected, and how this data is currently used.
Research Interests:
Pile settlement is a key geotechnical design consideration. The serviceability limit state for deep foundations cannot be ignored and yet many design methods merely assume that large factors of safety are sufficient to prevent excessive... more
Pile settlement is a key geotechnical design consideration. The serviceability limit state for deep foundations cannot be ignored and yet many design methods merely assume that large factors of safety are sufficient to prevent excessive settlements. A simple model, supported by previously published databases of load testing on bored piles founded in London clay, is used to make predictions of settlement for bored pile foundations in the same geological deposit. The results of a detailed sensitivity study of the key parameters that affect the performance of bored piled foundations are presented. The parameters studied include: the mobilisation factor; the mobilisation strain; the elastic modulus of the concrete; the undrained shear strength profile; the pile length and the pile diameter. Based on the preliminary results of this sensitivity study, design guidance is presented and a rank of order of the parameters is given in order of their influence on the settlement calculation result. The influence of soil non-linearity is also studied.
Research Interests:
Geotechnical Engineers should devote a considerable amount of time to understanding foundation settlements. When designing in soil deposits that are unfamiliar, pile load testing is essential for investigating likely foundation movements.... more
Geotechnical Engineers should devote a considerable amount of time to understanding foundation settlements. When designing in soil deposits that are unfamiliar, pile load testing is essential for investigating likely foundation movements. Simple models to compute pile settlement are also useful for design engineers, especially in soil deposits that are not widely studied or reported. Pile load test data is presented along with relevant site investigation data for a site in the Jurassic clay in Moscow. This clay is of similar age to the Oxford clay found in England. The available site investigation data included Atterberg limit tests and CPT tests. Settlement analysis is carried out from the load testing of 20m long circular bored piles in this stiff over-consolidated clay. A simple MSD-style settlement model was used to backanalyse the results of the load testing conducted at this site. The backanalysis results are compared against the general methods in Russian codes of practice (SNiP/SP). The prediction of pile settlements in Russia generally assumes use of numerical modelling or emprical calculations given in Russian codes of practice, and this paper provides an alternative approach based on a semi-empirical method.
Research Interests:
Many bridges across the world have very extensive structural health monitoring (SHM) systems that generate vast quantities of data. There are many engineers and researchers who envisage a brave new world of smart bridges with ubiquitous... more
Many bridges across the world have very extensive structural health monitoring (SHM) systems that generate vast quantities of data. There are many engineers and researchers who envisage a brave new world of smart bridges with ubiquitous sensors providing real time information on all aspects of bridge performance. How realistic is this aspiration? How do we currently utilise the data generated in existing bridge SHM systems? How are such SHM systems designed in the first place? A major research programme at the Centre for Smart Infrastructure and Construction (CSIC) at Cambridge University in the UK has been at the forefront of some of these smart technology developments, specifically in fibre optics, wireless sensor networks, MEMS sensors, computer vision techniques and data interpretation tools. A recent PhD study by Webb [10] in which he investigated the manner in which such monitoring systems are currently designed, deployed and utilised for bridges has led to a re-evaluation of their effectiveness. A new framework which provides guidance for bridge engineers on how to design such SHM systems has been developed and will be presented in this paper.
Research Interests:
The Atterberg Limits are the most common tests specified by practicing geotechnical and pavement engineers the world over. They are used to classify soils using the framework pioneered by Terzaghi and Casagrande during their work with the... more
The Atterberg Limits are the most common tests specified by practicing geotechnical and pavement engineers the world over. They are used to classify soils using the framework pioneered by Terzaghi and Casagrande during their work with the US Public Roads Bureau in the 1920s and 1930s and are also correlated with many fundamental soil parameters, used in design and construction projects. In the 21 st century the Atterberg Limits remain a key component of the testing armory of practicing geotechnical engineers as they can be obtained easily for the large numbers of samples that are needed on major construction projects and allow for rapid assessments of key soil parameters. Their fundamental definitions are worthy of review; the thread-rolling test for plastic limit has remained largely unchanged since Atterberg first described it in 1911 but the definition and measurement of liquid limit varies across the globe. The fundamental mechanics of the Casagrande Cup liquid limit have been the subject of recent study showing clearly that liquid limit determined in this way relates to a fixed value of specific soil strength (i.e. strength per unit density) as opposed to a fixed strength value when liquid limit is measured by the fall-cone method. These findings explain the deviation between liquid limits measured by the two methods for high plasticity soils without the need to invoke different strength regimes. The brittle failure mechanism in the thread-rolling test has also been recently reexamined. It is proposed that the brittle failure observed in the plastic limit test is caused by either air entry or cavitation in the clay and plastic limit and does not correspond to a fixed strength. The Atterberg Limits are used to compute liquidity index which is widely related to clay strength variation, this is critical for many areas of construction (especially when rapid assessments of strength are required). The Russian code for the design of piled foundations, for example, uses liquidity index values to assess shaft friction. Recent research outcomes at the University of Cambridge have challenged certain assumptions pertaining to widely-used correlations between liquidity index and undrained strength.
Research Interests:
This paper presents a study of the constraints and challenges faced by the authors when invited to study the feasibility of developing a monitoring system to provide specific information sought by the designer and contractor during the... more
This paper presents a study of the constraints and challenges faced by the authors when invited to study the feasibility of developing a monitoring system to provide specific information sought by the designer and contractor during the construction of the new 225m high, 48 storey steel-framed Leadenhall Building, located at 122 Leadenhall Street in London. The original goal of the study was to develop a system to assist with the active alignment of the building during construction, a key aim being to determine if the diagonal bracing members were in tension or compression. Installing strain gauges directly onto the steel bracing members was not permitted due to concerns regarding the integrity of the intumescent paint coating. A laboratory study to investigate the ability to measure strain directly from the paint surface was undertaken. Aesthetic concerns also imposed further restrictions on what could be attached to the structure. This feasibility study did result in the development of a new wireless sensor to measure temperature and optionally strain. In order to allow the sensors to be unobtrusive they were designed to fit within holes already present in the steel sections, originally used for attaching lifting equipment during erection of the steel frame. This exploratory study demonstrates that such collaborations can yield outcomes which, while not originally envisaged, nevertheless have the potential to benefit the research organisation, the designer and the contractor. This paper demonstrates how a bespoke wireless sensor platform can be rapidly developed using existing technologies to fit the needs of an individual project. The potential for use on future construction projects of a similar nature is also highlighted and future research directions discussed.
Research Interests:
When designing geotechnical structures engineers need to assign soil parameters. Soil design parameters are often inferred through correlations with basic site investigation data. The objective of this work is to determine the shape of... more
When designing geotechnical structures engineers need to assign soil parameters. Soil design parameters are often inferred through correlations with basic site investigation data. The objective of this work is to determine the shape of the undrained stress-strain curve of a heavily overconsolidated Eocene clay in such a way that it may conveniently be used in simplified deformation mechanisms to predict ground movements due to construction. A database of London clay triaxial test data is presented. Use of a power model to predict strength mobilization is demonstrated for 17 previously published triaxial tests on high quality cores of London clay. A novel method of normalising these mobilization curves is demonstrated (using a reference strain at 50% mobilization of shear strength), and different relations are shown to apply to different magnitudes of strain. The parameters that influence the variation of the reference strain are studied.
Research Interests:
The use of databases in geotechnical engineering allows engineers to make a priori estimates of soil behaviour. Based on a study of the published literature, a database of 20 clays and silts is presented that allows predictions to be made... more
The use of databases in geotechnical engineering allows engineers to make a priori estimates of soil behaviour. Based on a study of the published literature, a database of 20 clays and silts is presented that allows predictions to be made of the strain-dependent stiffness of fine-grained soils, based on simple soil parameters. The significance of rate effects is discussed and corrections are made. The use of a reference strain γ ref to normalize shear strain values γ in relation to modulus reduction G/G 0 is discussed. Empirical formulations are presented based on a rigorous regression analysis, and design charts are constructed.
Research Interests:
The design of piles in clay is an important engineering design task. This paper compares the effect two codes of practice and two calculation approaches have on the computed design capacity of a bored pile in London clay. It is shown that... more
The design of piles in clay is an important engineering design task. This paper compares the effect two codes of practice and two calculation approaches have on the computed design capacity of a bored pile in London clay. It is shown that the choice of a design line to describe the soil strength profile is the major factor that affects the length of pile required.
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This paper presents a discussion of “Uniqueness of suction stress value at liquid limit of soil” by Ning Lu, Angel Rodrigo Angulo Calderon and Alexandra Wayllace. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002937
Research Interests: Geotechnical Engineering, Soil Mechanics, Geotechnical Investigation, Soil and Rock Mechanics, Experimental investigation of the mechanical behaviour of soils, and 9 moreGeotechnics, Geotechnical Enginnering, Soil Suction, Determination of Liquid Limit Cone Penetrometer Method, Soil Foundations, Definición De Límite Líquido, Límites De Atterberg, Soils Mechanics, and Géotechnique
Research Interests: Geotechnical Engineering, Soil Mechanics, Geotechnical Investigation, Soil Investigation and Testing, Engineering Geology and Geotechnical Problems, and 14 moreExperimental investigation of the mechanical behaviour of soils, Geotechnics, Geotechnical Enginnering, Extrusion Processing, Extrusion, Workability, Determination of Liquid Limit Cone Penetrometer Method, Soil Foundations, Definición De Límite Líquido, Resistencia Al Cosrtante En El Límite Líquido, Límites De Atterberg, Soils Mechanics, Géotechnique, and Geological and Geotechnical Engineering
Free access to the full published article is provided until 17th May 2022 via the following Share Link: https://authors.elsevier.com/a/1epdM38lpJfN1 The Authors have presented an interesting paper (Hrubesova et al., 2020), which aims... more
Free access to the full published article is provided until 17th May 2022 via the following Share Link: https://authors.elsevier.com/a/1epdM38lpJfN1
The Authors have presented an interesting paper (Hrubesova et al., 2020), which aims (in part) to validate the Moharjerani (1999) calibration approach for establishing the 80 g/30◦ fall-cone penetration depth equating to the liquid limit by the Casagrande percussion-cup approach, determined according to the British Standard. In this paper, the Discussers present some clarifications on, and state various observations regarding, the approaches adopted in the Hrubesova et al. (2020) investigation, as well as the Moharjerani (1999) calibration approach employed therein. The Discussers also present a description of some relevant literature not covered in the Authors’ paper (Hrubesova et al. 2020) aimed at making further clarifications on this important area of geotechnical practice.
The Authors have presented an interesting paper (Hrubesova et al., 2020), which aims (in part) to validate the Moharjerani (1999) calibration approach for establishing the 80 g/30◦ fall-cone penetration depth equating to the liquid limit by the Casagrande percussion-cup approach, determined according to the British Standard. In this paper, the Discussers present some clarifications on, and state various observations regarding, the approaches adopted in the Hrubesova et al. (2020) investigation, as well as the Moharjerani (1999) calibration approach employed therein. The Discussers also present a description of some relevant literature not covered in the Authors’ paper (Hrubesova et al. 2020) aimed at making further clarifications on this important area of geotechnical practice.
Research Interests: Geotechnical Engineering, Soil Mechanics, Geotechnical Investigation, Engineering Geology and Geotechnical Problems, Experimental investigation of the mechanical behaviour of soils, and 7 moreGeotechnics, Determination of Liquid Limit Cone Penetrometer Method, Soil Foundations, Casagrande, Definición De Límite Líquido, Límites De Atterberg, and Géotechnique
Vardanega, P.J., Haigh, S.K., O’Kelly, B.C., Zhang, X., Liu, X., Chen, C. & Wang, G. (2022). Discussion: Use of fall-cone flow index for soil classification: a new plasticity chart. Géotechnique, https://doi.org/10.1680/jgeot.21.00268
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Vardanega, P.J. (2021). Editorial. Proceedings of the Institution of Civil Engineers – Engineering Sustainability, 174(5): 211-212 https://doi.org/10.1680/jensu.2021.174.5.211
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The undrained shear strength of soil is a key engineering parameter, which is often linked to liquidity index (e.g. Vardanega and Haigh 2014). This linkage depends critically on the undrained strength of soil at the liquid limit, a... more
The undrained shear strength of soil is a key engineering parameter, which is often linked to liquidity index (e.g. Vardanega and Haigh 2014). This linkage depends critically on the undrained strength of soil at the liquid limit, a subject on which there has been some debate. The determination of the liquid limit is carried out using one of two general methods: ‘Casagrande cup’ or ‘fall cone’, depending on national standards. The authors have presented an interesting paper that shows (amongst other things) how fall-cone undrained shear strength values at the fall-cone liquid limit (cuFC;LL) can vary with changes in the water content at the fall-cone liquid limit (wL;FC ). Data of the undrained strength at liquid limit when this is determined by the fall cone are rare, although since this test is itself a measurement of soil strength, examination typically shows a much narrower range of values than for strengths measured at the Casagrande-cup liquid limit (wL;cup ). It is hence surprising that the work of Nagaraj et al. (2018) shows such clear trends of varying undrained strength at the fall-cone liquid limit with water content. The paper hence prompts a debate as to whether the undrained strength at the fall-cone liquid limit can be sensibly assumed as a fixed value. This discussion seeks (in the context of the published paper) to explore this question.
Research Interests: Soil Science, Geotechnical Engineering, Soil Mechanics, Geotechnical Investigation, Engineering Geology and Geotechnical Problems, and 10 moreSoil Behavior, Geotechnics, Geotechnical Enginnering, Determination of Liquid Limit Cone Penetrometer Method, Soil Foundations, Definición De Límite Líquido, Límites De Atterberg, Soils Mechanics, Géotechnique, and Geological and Geotechnical Engineering
Vardanega, P.J., Moinet, W.W. & Castellanza, R. (2021). Editorial. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 174(4): 331–333 https://doi.org/10.1680/jgeen.2021.174.4.331
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Vardanega, P.J., Elia, G. & Yao, K. (2021). Editorial. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 174(2): 99–101 https://doi.org/10.1680/jgeen.2021.174.2.99
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Feng, S., Vardanega, P.J., Ibraim, E., Widyatmoko, I., Ojum, C., O'Kelly, B.C. & Nogal, M. (2020). Discussion: Permeability assessment of some granular mixtures. Géotechnique, 70(9): 845–847 https://doi.org/10.1680/jgeot.19.d.005
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Research Interests: Geotechnical Engineering, Soil Mechanics, Geotechnical Investigation, Engineering Geology and Geotechnical Problems, Experimental investigation of the mechanical behaviour of soils, and 8 moreGeotechnics, Shear Strength, Determination of Liquid Limit Cone Penetrometer Method, Soil Foundations, Definición De Límite Líquido, Resistencia Al Cosrtante En El Límite Líquido, Plastic Limit Load, and Géotechnique
O’Kelly, B.C., Vardanega, P.J., Haigh, S.K. & Barnes, G.E. (2020). Discussion: Use of fall cones to determine Atterberg limits: a review. Géotechnique, 70(7): 647-651 https://doi.org/10.1680/jgeot.19.d.003
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Vardanega, P.J. (2020). Editorial. Proceedings of the Institution of Civil Engineers – Engineering Sustainability, 173(3): 107-108 https://doi.org/10.1680/jensu.2020.173.3.107
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Vardanega, P.J., O’Kelly, B.C. & Haigh, S.K. (2020). Discussion of “Reclaimed Lignin-Stabilized Silty Soil: Undrained Shear Strength, Atterberg Limits, and Microstructure Characteristics” by Tao Zhang, Guojun Cai, and Songyu Liu. Journal... more
Vardanega, P.J., O’Kelly, B.C. & Haigh, S.K. (2020). Discussion of “Reclaimed Lignin-Stabilized Silty Soil: Undrained Shear Strength, Atterberg Limits, and Microstructure Characteristics” by Tao Zhang, Guojun Cai, and Songyu Liu. Journal of Materials in Civil Engineering (ASCE), 32(3): [07020001] https://doi.org/10.1061/(ASCE)MT.1943-5533.0003064
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Vardanega, P.J. (2020). Editorial. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 173(1): 1-2 https://doi.org/10.1680/jgeen.2020.173.1.1
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Vardanega, P.J. (2019). Editorial. Proceedings of the Institution of Civil Engineers – Engineering Sustainability, 172(8): 415 https://doi.org/10.1680/jensu.2019.172.8.415
Go, J. & Vardanega, P.J. (2019). Editorial. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 172(1): 1-3 https://doi.org/10.1680/jgeen.2019.172.1.1
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Vardanega, P.J. & Haigh, S.K. (2017). Discussion of "Water Content Ratio: An Effective Substitute for Liquidity Index for Prediction of Shear Strength of Clays" by Beshy Kuriakose, Benny Mathews Abraham, A. Sridharan & Babu T. Jose.... more
Vardanega, P.J. & Haigh, S.K. (2017). Discussion of "Water Content Ratio: An Effective Substitute for Liquidity Index for Prediction of Shear Strength of Clays" by Beshy Kuriakose, Benny Mathews Abraham, A. Sridharan & Babu T. Jose. Geotechnical and Geological Engineering, 35(6): 3039-3044 https://doi.org/10.1007/s10706-017-0290-0
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Pollock-Fraser, H., Christopher, P., Kennedy, C., Webster, T., Vardanega, P.J., Johansson, A. & Cottrell, R. (2017). Discussion: A new tram network for Bristol: a possible solution? Proceedings of the Institution of Civil Engineers -... more
Pollock-Fraser, H., Christopher, P., Kennedy, C., Webster, T., Vardanega, P.J., Johansson, A. & Cottrell, R. (2017). Discussion: A new tram network for Bristol: a possible solution? Proceedings of the Institution of Civil Engineers - Municipal Engineer, 170(3): 185 https://doi.org/10.1680/jmuen.17.00013
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Vardanega, P.J. (2017). Editorial. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 170(2): 95-96 https://doi.org/10.1680/jgeen.2017.170.2.95
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Vardanega, P.J., Webb, G.T., Fidler, P.R.A., Middleton, C.R. & Collins, J. (2017). Discussion: Assessing the potential value of bridge monitoring systems. Proceedings of the Institution of Civil Engineers – Bridge Engineering, 170(1):... more
Vardanega, P.J., Webb, G.T., Fidler, P.R.A., Middleton, C.R. & Collins, J. (2017). Discussion: Assessing the potential value of bridge monitoring systems. Proceedings of the Institution of Civil Engineers – Bridge Engineering, 170(1): 87-88 https://doi.org/10.1680/jbren.16.00027
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Vardanega, P.J. & Bolton, M.D. (2016). Discussion of “Undrained Young’s Modulus of Fine-Grained Soils” by B. Casey, J. T. Germaine, N. O. Abdulhadim, N. S. Kontopoulos and C. A. Jones. Journal of Geotechnical and Geoenvironmental... more
Vardanega, P.J. & Bolton, M.D. (2016). Discussion of “Undrained Young’s Modulus of Fine-Grained Soils” by B. Casey, J. T. Germaine, N. O. Abdulhadim, N. S. Kontopoulos and C. A. Jones. Journal of Geotechnical and Geoenvironmental Engineering (ASCE), 142(10): [07016023] https://doi.org/10.1061/(ASCE)GT.1943-5606.0001571
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Sivakumar V, O'Kelly BC, Henderson L, Moorhead C, Chow SH, Haigh SK and Vardanega PJ (2016) Discussion: Measuring the plastic limit of fine soils: an experimental study. Proceedings of the Institution of Civil Engineers, Geotechnical... more
Sivakumar V, O'Kelly BC, Henderson L, Moorhead C, Chow SH, Haigh SK and Vardanega PJ (2016) Discussion: Measuring the plastic limit of fine soils: an experimental study. Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, vol. 169, issue 1, pages 86–89. http://dx.doi.org/10.1680/jgeen.15.00090
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Vardanega, P.J. & Bolton, M.D. (2016). Discussion of “Characterization of Model Uncertainty for Cantilever Deflections in Undrained Clay” by D.M. Zhang, K.K. Phoon, H.W. Huang and Q.F. Hu. Journal of Geotechnical and Geoenvironmental... more
Vardanega, P.J. & Bolton, M.D. (2016). Discussion of “Characterization of Model Uncertainty for Cantilever Deflections in Undrained Clay” by D.M. Zhang, K.K. Phoon, H.W. Huang and Q.F. Hu. Journal of Geotechnical and Geoenvironmental Engineering (ASCE), 142(1): [07015036] https://doi.org/10.1061/(ASCE)GT.1943-5606.0001395
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Vardanega, P.J. & Waters, T.J. (2015). Discussion of "Evaluating the relationship between permeability and moisture damage of asphalt concrete pavements" by Rafiqul A. Tarefder and Mohiuddin Ahmad. Journal of Materials in Civil... more
Vardanega, P.J. & Waters, T.J. (2015). Discussion of "Evaluating the relationship between permeability and moisture damage of asphalt concrete pavements" by Rafiqul A. Tarefder and Mohiuddin Ahmad. Journal of Materials in Civil Engineering (ASCE), 27(12): [07015009] https://doi.org/10.1061/(ASCE)MT.1943-5533.0001411
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Haigh, S.K., Vardanega, P.J., Bolton, M.D. & Barnes, G.E. (2014). Discussion: The Plastic Limit of Clays. Géotechnique, 64(7): 584-586 https://doi.org/10.1680/geot.13.D.06
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Vardanega, P.J. (2014). Discussion of “A New Model on the Hydraulic Conductivity of Asphalt Mixtures” by J. Norambuena-Contreras, E. Asanza Izquierdo, D. Castro-Fresno, Manfred N. Partl and Alvaro Garcia. International Journal of Pavement... more
Vardanega, P.J. (2014). Discussion of “A New Model on the Hydraulic Conductivity of Asphalt Mixtures” by J. Norambuena-Contreras, E. Asanza Izquierdo, D. Castro-Fresno, Manfred N. Partl and Alvaro Garcia. International Journal of Pavement Research and Technology, 7(3): 223-224.
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Orr, T.L.L. & Vardanega, P.J. (2013). Discussion: How Eurocode 7 has affected geotechnical design: a review. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 166(6): 610-612 https://doi.org/10.1680/geng.13.00011
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Vinod, P., Sridharan, A., Deepa, K.A., Haigh, S.K. & Vardanega, P.J. (2013). Discussion: Remoulded shear strength at plastic and semi-solid states. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 166(5):... more
Vinod, P., Sridharan, A., Deepa, K.A., Haigh, S.K. & Vardanega, P.J. (2013). Discussion: Remoulded shear strength at plastic and semi-solid states. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering, 166(5): 515-517 https://doi.org/10.1680/geng.12.00093
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Vardanega, P.J., Lau, B.H., Lam, S.Y., Haigh, S.K., Madabhushi, S.P.G., Bolton, M.D. & Mayne, P.W. (2013). Discussion: Laboratory measurement of strength mobilization in kaolin: link to stress history. Géotechnique Letters, 3(1): 16-17... more
Vardanega, P.J., Lau, B.H., Lam, S.Y., Haigh, S.K., Madabhushi, S.P.G., Bolton, M.D. & Mayne, P.W. (2013). Discussion: Laboratory measurement of strength mobilization in kaolin: link to stress history. Géotechnique Letters, 3(1): 16-17 https://doi.org/10.1680/geolett.13.00005
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Haigh, S.K. & Vardanega, P.J. (2012) Discussion of “Re-examination of undrained strength at Atterberg Limits Water Contents” by H. B. Nagaraj, A. Sridharan and H. M. Mallikarjuna. Geotechnical and Geological Engineering, 30(6): 1389-1391... more
Haigh, S.K. & Vardanega, P.J. (2012) Discussion of “Re-examination of undrained strength at Atterberg Limits Water Contents” by H. B. Nagaraj, A. Sridharan and H. M. Mallikarjuna. Geotechnical and Geological Engineering, 30(6): 1389-1391 https://doi.org/10.1007/s10706-012-9543-0
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Structural health monitoring (SHM) has the potential to transform the bridge engineering industry by providing stakeholders with additional information to inform decisions about the design, operation, and management of bridges throughout... more
Structural health monitoring (SHM) has the potential to transform the bridge engineering industry by providing stakeholders with additional information to inform decisions about the design, operation, and management of bridges throughout their life. This chapter gives guidance on SHM for engineers who design, build, operate and maintain bridges. There remain numerous technical challenges to overcome when deploying SHM systems, but the most important issues to be considered are how to decide what information is required and then how to develop a strategy to deliver this information in a form that is easy to interpret so as to inform decision making. This chapter presents a series of case studies to show how SHM systems can be used in practice to obtain valuable data and to explore the challenges faced during such projects. Future directions for emerging technologies and approaches for future research and management of bridge SHM systems are also discussed.
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This report outlines the database of pile load test information that has been built as part of the Engineering and Physical Sciences Research Council (EPSRC) funded project EP/P020933/1: Databases to INterrogate Geotechnical Observations... more
This report outlines the database of pile load test information that has been built as part of the Engineering and Physical Sciences Research Council (EPSRC) funded project EP/P020933/1: Databases to INterrogate Geotechnical Observations (DINGO) which ran between 1 July 2017 and 9 June 2019. The database is populated with data digitised from the literature as well as datasets supplied by contributors from the geotechnical engineering industry in the United Kingdom. The database file structure is inspired by the AGS data format (Association of Geotechnical and Geoenvironmental Engineering Specialists). The report is arranged in five main parts: (1) In the first section the background and rationale of the project is explained in detail; (2) In the second section the methodology and tools used by the research team to build the database are explained; (3) In the third section the database structure is shown and commentary is given for those wishing to download some or all of the information contained in the DINGO database; (4) In this section preliminary analysis of the collected data is represented on a series of maps, drawn using a geographical information system (GIS), which show the following subsets: (a) construction era; (b) pile foundation typology; (c) geological deposit and soil characteristics; (5) The report concludes with a summary as well as a series of appendices and references that in part explain the structure, arrangement and origin of the information in the DINGO database. The database has been uploaded to the data.bris Research Data Repository at the University of Bristol, and has been released online (https://doi.org/10.5523/bris.89r3npvewel2ea8ttb67ku4d) for use by the community under the CC-BY 4.0 Licence (https://creativecommons.org/licenses/by/4.0/)
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This report outlines the database of pile load test information that has been built as part of the Engineering and Physical Sciences Research Council (EPSRC) funded project EP/P020933/1: Databases to INterrogate Geotechnical Observations... more
This report outlines the database of pile load test information that has been built as part of the Engineering and Physical Sciences Research Council (EPSRC) funded project EP/P020933/1: Databases to INterrogate Geotechnical Observations (DINGO) which ran between 1 July 2017 and 9 June 2019. The database is populated with data digitised from the literature as well as datasets supplied by contributors from the geotechnical engineering industry in the United Kingdom. The database file structure is inspired by the AGS data format (Association of Geotechnical and Geoenvironmental Engineering Specialists). The report is arranged in five main parts: (1) In the first section the background and rationale of the project is explained in detail; (2) In the second section the methodology and tools used by the research team to build the database are explained; (3) In the third section the database structure is shown and commentary is given for those wishing to download some or all of the information contained in the DINGO database; (4) In this section preliminary analysis of the collected data is represented on a series of maps, drawn using a geographical information system (GIS), which show the following subsets: (a) construction era; (b) pile foundation typology; (c) geological deposit and soil characteristics; (5) The report concludes with a summary as well as a series of appendices and references that in part explain the structure, arrangement and origin of the information in the DINGO database. The database has been uploaded to the data.bris Research Data Repository at the University of Bristol, and has been released online (https://doi.org/10.5523/bris.3r14qbdhv648b2p83gjqby2fl8) for use by the community under the CC-BY 4.0 Licence (https://creativecommons.org/licenses/by/4.0/)
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Supplementary material 2 for "Hydraulic conductivity of fine-grained soils subjected to freeze-thaw cycles"
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Supplementary material 1 for "Hydraulic conductivity of fine-grained soils subjected to freeze-thaw cycles"
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Supplementary data for "Use of hydraulic radius to estimate the permeability of coarse-grained materials using a new geodatabase"
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Paul Vardanega, Elia Voyagaki, Jamie Crispin, Charlotte Gilder, Konstantina Ntasiou (2021): The DINGO Database, v1.1. https://doi.org/10.5523/bris.89r3npvewel2ea8ttb67ku4d
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Paul Vardanega, Elia Voyagaki, Jamie Crispin, Charlotte Gilder, Konstantina Ntasiou (2019): The DINGO Database, v1.0. https://doi.org/10.5523/bris.3r14qbdhv648b2p83gjqby2fl8
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ONLINE SUPPLEMENT
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ONLINE SUPPLEMENT: EXAMPLE GRADING ENTROPY CALCULATION
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Online Supplement – CHASM Model Parameters