Journal of Geotechnical and Geoenvironmental Engineering, 2009
ABSTRACT The undrained remolded shear strength of soft clays is of importance in geosystem design... more ABSTRACT The undrained remolded shear strength of soft clays is of importance in geosystem design, particularly for offshore structures. Common methods to estimate remolded shear strength, such as correlations with cone penetration data, direct measurement with an in situ field vane shear device, and laboratory measurements, produce varied results and can be particularly costly and time consuming. Full-flow penetrometers (T-bar and Ball) provide an alternative rapid method to estimate remolded shear strength and soil sensitivity through remolding soil by repeated cycling of the penetrometer up and down over a given depth interval. The cyclic penetration resistance degradation curve inherently contains information regarding remolded strength and sensitivity. The objective of this paper is to assess the ability of full-flow penetrometers to predict remolded strength and soil sensitivity, and to develop a suite of predictive correlations in which these properties can be estimated in the absence of complementary laboratory or in situ test data. To accomplish this, full-flow penetration profiles and cyclic tests were performed at five well characterized soft clay sites, which together represent the broad range of soils in which the penetrometers will be often used. A previously developed model for the reduction in penetration resistance with cycling is modified to predict the entire degradation curve, including the remolded penetration resistance using only measurements obtained during initial penetrometer penetration and extraction. Using field vane shear strength as the reference measurement, correlations are developed to predict soil sensitivity and remolded shear strength based solely on full-flow penetrometer data, which is particularly useful in site investigation programs where site specific data are not yet available or are sparse. Finally, the usefulness of these relationships is demonstrated by implementing them for two additional soft clay sites.
Journal of Geotechnical and Geoenvironmental Engineering, 2009
ABSTRACT This paper presents a numerical investigation of the effect of foundation size on the re... more ABSTRACT This paper presents a numerical investigation of the effect of foundation size on the response of shallow circular foundations on siliceous and calcareous sands. The study is based on the predictive capabilities of the MIT-S1 soil model for simulating both the compression and shear behaviors of natural sands over a wide range of densities, K(0) values and confining pressures. The paper highlights the variations in the deformation mechanisms for the siliceous and calcareous sands cases. The assessment of the bearing capacity factor, N(gamma), is examined, showing a dramatic decrease in the values with increasing foundation size for the case of footings on calcareous sands, eventually converging to a terminal N(gamma) value. At this stage the sand resistance is insensitive to variations in initial density and foundation size because the sand tends to loose its initial characteristics due to grain crushing, leading the material rapidly toward ultimate conditions. In the silicious sand case, it is found that, eventually, for extremely large footing diameters, the deformation mechanism progresses toward a punching shear mechanism, rather than the classical rapture pattern accompanied by surface heave as employed in current bearing capacity equations. A dimensional transition between the failure mechanisms can clearly be defined, referred to as a "critical size" in the N(gamma)-D relationship.
Journal of Geotechnical and Geoenvironmental Engineering, 2008
... In this study, the continuous pullout of circular anchors in NC soil was investigated using F... more ... In this study, the continuous pullout of circular anchors in NC soil was investigated using FE ... to a constant value (the “deep” limit of ) until , after which the normalized load increases continuously ... degree of suction below the anchor will be needed for the full deep capacity of the ...
Journal of Geotechnical and Geoenvironmental Engineering, 2008
... In this study, the continuous pullout of circular anchors in NC soil was investigated using F... more ... In this study, the continuous pullout of circular anchors in NC soil was investigated using FE ... to a constant value (the “deep” limit of ) until , after which the normalized load increases continuously ... degree of suction below the anchor will be needed for the full deep capacity of the ...
Journal of Geotechnical and Geoenvironmental Engineering, 2011
A series of centrifuge model tests of the lateral response of a fixed-head single pile in soft cl... more A series of centrifuge model tests of the lateral response of a fixed-head single pile in soft clay is reported. Both monotonic and cyclic episodes of loading are described, with varying amplitude and with intervening periods of reconsolidation. The soil conditions are characterized by cyclic T-bar penetrometer tests. The ultimate capacity under monotonic load for virgin and for postcyclic conditions was found to be comparable with calculations based on existing design methods, including theoretical plasticity solutions and empirical methods. The lateral stiffness was observed to degrade with cycles, with the rate of degradation being greater for larger cycles. The degradation pattern has been tentatively linked to the cyclic T-bar response, by considering the ‘damage’ associated with the cumulative displacement and remolding, in each case. This approach provides a consistent interpretation of the tests. Although episodes of pile movement and soil remolding led to a reduction in lateral resistance, interv...
Journal of Geotechnical and Geoenvironmental Engineering, 2001
This paper describes the results of a centrifuge modeling study of the response of piles embedded... more This paper describes the results of a centrifuge modeling study of the response of piles embedded in calcareous sand under monotonic lateral loading. A number of features have been explored, including method of installation, rate of loading, and pile head restraint. The study has led to recommendations for load-transfer curves with the magnitude of lateral resistance linked to the soil strength through the cone resistance. Modification factors have been developed to allow for different methods of installation and for different rates of loading. The proposed load-transfer curves and resulting pile response are shown to provide an excellent match with the experimental data, and are compared with results derived using existing guidelines for terrigenous sands. Significant differences are demonstrated, confirming the need to treat calcareous sediments separately from other soil types with respect to lateral pile response.
A new method is proposed for deriving kinematically admissible velocity fields (KAVFs) for three-... more A new method is proposed for deriving kinematically admissible velocity fields (KAVFs) for three-dimensional upper bound limit analyses in a Tresca material using coordinate transformations. The method allows the incompressibility condition to be satisfied simply by imposing certain requirements on the analytical form of velocity magnitudes. This allows for new classes of velocity fields to be derived solely using standard procedures. These new classes of fields include: KAVFs with new streamline shapes; new planar but non-plane-strain KAVFs; new radial but nonaxisymmetric KAVFs. The method allows the expression of local dissipation of plastic work in any field to be derived in a closed form. The proposed method makes an attempt to expand the applicability of three-dimensional upper bound limit analysis by introducing more realistic shapes of KAVFs, while maintaining simplicity and clear engineering meaning.
... The uniaxial vertical bearing capacity of square and rectangular footings resting on homogene... more ... The uniaxial vertical bearing capacity of square and rectangular footings resting on homogeneous undrained clay is investigated with finite element analyses, using both Tresca and von Mises soil models. ... Comparison of Bearing Capacity Predictions with Tresca and von Mises. ...
Effect of Strain Rate and Strain Softening on the Penetration Resistance of Spudcan Foundations o... more Effect of Strain Rate and Strain Softening on the Penetration Resistance of Spudcan Foundations on Clay. [International Journal of Geomechanics 9, 122 (2009)]. Muhammad Shazzad Hossain, Mark F. Randolph. Abstract. In practice ...
Submarine landslides represent one of the most significant geohazards on the continental slope in... more Submarine landslides represent one of the most significant geohazards on the continental slope in respect of the risk they pose to infrastructure such as deep water pipelines. A numerical approach, based on the finite-element method but using remeshing, was established in this paper to simulate large flow deformation of debris from a landslide and to quantify the loads and displacements imposed on pipelines embedded in the seabed. A simple two-dimensional elastic perfectly plastic soil model with plane strain conditions was employed in this analysis. The pipeline was restrained by a set of springs so that the load on the pipeline built up to a stable value, representing the limiting load at which the debris flowed over the pipeline. A parametric study was undertaken by varying the pipeline embedment and the relative strengths of the debris and seabed. The analysis results show that the various combinations of soil strength and embedment depth lead to different debris-pipeline movement patterns and consequ...
Journal of Geotechnical and Geoenvironmental Engineering, 2009
ABSTRACT The undrained remolded shear strength of soft clays is of importance in geosystem design... more ABSTRACT The undrained remolded shear strength of soft clays is of importance in geosystem design, particularly for offshore structures. Common methods to estimate remolded shear strength, such as correlations with cone penetration data, direct measurement with an in situ field vane shear device, and laboratory measurements, produce varied results and can be particularly costly and time consuming. Full-flow penetrometers (T-bar and Ball) provide an alternative rapid method to estimate remolded shear strength and soil sensitivity through remolding soil by repeated cycling of the penetrometer up and down over a given depth interval. The cyclic penetration resistance degradation curve inherently contains information regarding remolded strength and sensitivity. The objective of this paper is to assess the ability of full-flow penetrometers to predict remolded strength and soil sensitivity, and to develop a suite of predictive correlations in which these properties can be estimated in the absence of complementary laboratory or in situ test data. To accomplish this, full-flow penetration profiles and cyclic tests were performed at five well characterized soft clay sites, which together represent the broad range of soils in which the penetrometers will be often used. A previously developed model for the reduction in penetration resistance with cycling is modified to predict the entire degradation curve, including the remolded penetration resistance using only measurements obtained during initial penetrometer penetration and extraction. Using field vane shear strength as the reference measurement, correlations are developed to predict soil sensitivity and remolded shear strength based solely on full-flow penetrometer data, which is particularly useful in site investigation programs where site specific data are not yet available or are sparse. Finally, the usefulness of these relationships is demonstrated by implementing them for two additional soft clay sites.
Journal of Geotechnical and Geoenvironmental Engineering, 2009
ABSTRACT This paper presents a numerical investigation of the effect of foundation size on the re... more ABSTRACT This paper presents a numerical investigation of the effect of foundation size on the response of shallow circular foundations on siliceous and calcareous sands. The study is based on the predictive capabilities of the MIT-S1 soil model for simulating both the compression and shear behaviors of natural sands over a wide range of densities, K(0) values and confining pressures. The paper highlights the variations in the deformation mechanisms for the siliceous and calcareous sands cases. The assessment of the bearing capacity factor, N(gamma), is examined, showing a dramatic decrease in the values with increasing foundation size for the case of footings on calcareous sands, eventually converging to a terminal N(gamma) value. At this stage the sand resistance is insensitive to variations in initial density and foundation size because the sand tends to loose its initial characteristics due to grain crushing, leading the material rapidly toward ultimate conditions. In the silicious sand case, it is found that, eventually, for extremely large footing diameters, the deformation mechanism progresses toward a punching shear mechanism, rather than the classical rapture pattern accompanied by surface heave as employed in current bearing capacity equations. A dimensional transition between the failure mechanisms can clearly be defined, referred to as a "critical size" in the N(gamma)-D relationship.
Journal of Geotechnical and Geoenvironmental Engineering, 2008
... In this study, the continuous pullout of circular anchors in NC soil was investigated using F... more ... In this study, the continuous pullout of circular anchors in NC soil was investigated using FE ... to a constant value (the “deep” limit of ) until , after which the normalized load increases continuously ... degree of suction below the anchor will be needed for the full deep capacity of the ...
Journal of Geotechnical and Geoenvironmental Engineering, 2008
... In this study, the continuous pullout of circular anchors in NC soil was investigated using F... more ... In this study, the continuous pullout of circular anchors in NC soil was investigated using FE ... to a constant value (the “deep” limit of ) until , after which the normalized load increases continuously ... degree of suction below the anchor will be needed for the full deep capacity of the ...
Journal of Geotechnical and Geoenvironmental Engineering, 2011
A series of centrifuge model tests of the lateral response of a fixed-head single pile in soft cl... more A series of centrifuge model tests of the lateral response of a fixed-head single pile in soft clay is reported. Both monotonic and cyclic episodes of loading are described, with varying amplitude and with intervening periods of reconsolidation. The soil conditions are characterized by cyclic T-bar penetrometer tests. The ultimate capacity under monotonic load for virgin and for postcyclic conditions was found to be comparable with calculations based on existing design methods, including theoretical plasticity solutions and empirical methods. The lateral stiffness was observed to degrade with cycles, with the rate of degradation being greater for larger cycles. The degradation pattern has been tentatively linked to the cyclic T-bar response, by considering the ‘damage’ associated with the cumulative displacement and remolding, in each case. This approach provides a consistent interpretation of the tests. Although episodes of pile movement and soil remolding led to a reduction in lateral resistance, interv...
Journal of Geotechnical and Geoenvironmental Engineering, 2001
This paper describes the results of a centrifuge modeling study of the response of piles embedded... more This paper describes the results of a centrifuge modeling study of the response of piles embedded in calcareous sand under monotonic lateral loading. A number of features have been explored, including method of installation, rate of loading, and pile head restraint. The study has led to recommendations for load-transfer curves with the magnitude of lateral resistance linked to the soil strength through the cone resistance. Modification factors have been developed to allow for different methods of installation and for different rates of loading. The proposed load-transfer curves and resulting pile response are shown to provide an excellent match with the experimental data, and are compared with results derived using existing guidelines for terrigenous sands. Significant differences are demonstrated, confirming the need to treat calcareous sediments separately from other soil types with respect to lateral pile response.
A new method is proposed for deriving kinematically admissible velocity fields (KAVFs) for three-... more A new method is proposed for deriving kinematically admissible velocity fields (KAVFs) for three-dimensional upper bound limit analyses in a Tresca material using coordinate transformations. The method allows the incompressibility condition to be satisfied simply by imposing certain requirements on the analytical form of velocity magnitudes. This allows for new classes of velocity fields to be derived solely using standard procedures. These new classes of fields include: KAVFs with new streamline shapes; new planar but non-plane-strain KAVFs; new radial but nonaxisymmetric KAVFs. The method allows the expression of local dissipation of plastic work in any field to be derived in a closed form. The proposed method makes an attempt to expand the applicability of three-dimensional upper bound limit analysis by introducing more realistic shapes of KAVFs, while maintaining simplicity and clear engineering meaning.
... The uniaxial vertical bearing capacity of square and rectangular footings resting on homogene... more ... The uniaxial vertical bearing capacity of square and rectangular footings resting on homogeneous undrained clay is investigated with finite element analyses, using both Tresca and von Mises soil models. ... Comparison of Bearing Capacity Predictions with Tresca and von Mises. ...
Effect of Strain Rate and Strain Softening on the Penetration Resistance of Spudcan Foundations o... more Effect of Strain Rate and Strain Softening on the Penetration Resistance of Spudcan Foundations on Clay. [International Journal of Geomechanics 9, 122 (2009)]. Muhammad Shazzad Hossain, Mark F. Randolph. Abstract. In practice ...
Submarine landslides represent one of the most significant geohazards on the continental slope in... more Submarine landslides represent one of the most significant geohazards on the continental slope in respect of the risk they pose to infrastructure such as deep water pipelines. A numerical approach, based on the finite-element method but using remeshing, was established in this paper to simulate large flow deformation of debris from a landslide and to quantify the loads and displacements imposed on pipelines embedded in the seabed. A simple two-dimensional elastic perfectly plastic soil model with plane strain conditions was employed in this analysis. The pipeline was restrained by a set of springs so that the load on the pipeline built up to a stable value, representing the limiting load at which the debris flowed over the pipeline. A parametric study was undertaken by varying the pipeline embedment and the relative strengths of the debris and seabed. The analysis results show that the various combinations of soil strength and embedment depth lead to different debris-pipeline movement patterns and consequ...
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Papers by Mark Randolph