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The assessment of the strain rate effect on the geotechnical properties of soils constitutes an important step toward a more accurate analysis of their response. This study presents the experimental results of monotonic and cyclic simple... more
The assessment of the strain rate effect on the geotechnical properties of soils constitutes an important step toward a more accurate analysis of their response. This study presents the experimental results of monotonic and cyclic simple shear tests performed to examine the strain rate ([Formula: see text]) effect on the behavior of eastern Canada soils. Nine natural soils sampled from different locations in eastern Canada were used in this study. The tests were performed on a simple shear device using a strain-controlled mode. In addition to the obtained experimental results, published data in the literature were used to draw the conclusions of this study. Analysis of the data indicates that the undrained shear strength (τf) increases proportionally with the strain rate by approximately 6%–17% per log cycle of [Formula: see text]. The results also show that the secant shear modulus G increases with the strain rate, especially at large strain amplitudes. Moreover, the analysis of th...
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On 25 November 1988, after the Saguenay earthquake, a landslide occurred in the municipality of Saint-Adelphe. The soil profile indicated that the deposit was composed of a stiff clay crustal layer overlying sensitive plastic clay with a... more
On 25 November 1988, after the Saguenay earthquake, a landslide occurred in the municipality of Saint-Adelphe. The soil profile indicated that the deposit was composed of a stiff clay crustal layer overlying sensitive plastic clay with a soft-to-stiff consistency. A geotechnical investigation was carried out in situ and in the laboratory and included the use of a new seismic simulator to develop a geotechnical model of the Saint-Adelphe clay. The model was incorporated in a finite-difference slope stability analysis before and during the earthquake. The results showed the development of plastic zones and the generation of pore water pressure, but the global safety factor remained above unity. A post-seismic analysis that utilized a strain-softening behavior model showed the initiation and propagation of the plastic zone, as well as the development of a failure surface close to the observed failure surface. Therefore, it is proposed that the Saint-Adelphe landslide could be explained...
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This study investigated a new predictive model of the shear modulus reduction () and damping ratio () curves for sensitive eastern Canada clays. The model was established based on experimental measurements of and performed on 69 sensitive... more
This study investigated a new predictive model of the shear modulus reduction () and damping ratio () curves for sensitive eastern Canada clays. The model was established based on experimental measurements of and performed on 69 sensitive clay specimens from eastern Canada. The compiled database was first analyzed to qualitatively assess the influences of different soil parameters on the measurements. Next, statistical analyses using regression analysis and the modified hyperbolic model were performed. It was found that the and values of sensitive eastern Canada clays were influenced mainly by the plasticity index (Ip), mean effective stress , and structure, which was quantified by the liquidity index (IL). Based on the statistical analysis performed, new equations for and were proposed. The newly proposed model was compared with previously published models. The comparison clearly showed that the proposed model was more representative of sensitive eastern Canada clays. Consequently,...
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Porous stones are commonly used in geotechnical laboratory testing to provide solid support at the two ends of the tested specimen. Although porous stones can have several advantages, they can induce a hydraulic impedance that might alter... more
Porous stones are commonly used in geotechnical laboratory testing to provide solid support at the two ends of the tested specimen. Although porous stones can have several advantages, they can induce a hydraulic impedance that might alter the flowrate results. Numerous suggestions and recommendations were issued to avoid some of the problems encountered when using porous stones, such as clogging and stones' low permeability coefficient (Kp). However, it is proven in this technical note that the existence of a soil-porous stones interaction prevents the elimination of porous stones' influence, leading to unreliable permeability results. A practical solution based on manufacturing unique porous stones (MS) is suggested in an attempt to eliminate such an influence. The porous stones influence is highlighted by running excess pore pressure dissipation tests in Triaxial conditions with calibrated beads. The results show a soil-porous stones interaction and a flowrate increase up ...
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Abstract Although much has been discussed on the liquefaction phenomenon and cyclic behavior of saturated sands, relatively little has been clarified on the difference between their cyclic behavior...
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ABSTRACT:Peck (1990) suggests that “defense in depth should remain a guiding principle for all designers of dams.” To act on this suggestion, we propose a new tool (which we call SIMSOLS) for examining the process of particle migration... more
ABSTRACT:Peck (1990) suggests that “defense in depth should remain a guiding principle for all designers of dams.” To act on this suggestion, we propose a new tool (which we call SIMSOLS) for examining the process of particle migration through porous media in a discrete manner. We use a EulerLagrange formulation to simulate flow and particle migration. This tool, which is currently in development, has been validated to demonstrate the applicability, accuracy, and usefulness of its results. Some 2D and 3D numerical results are presented and compared to those obtained experimentally, and they show good agreement. The ability of SIMSOLS to visualize flow in a porous medium and to study the particle migration process will make it a useful tool to help us understand the internal stability problem encountered in modern earth dams and levees built using soils with a potential for internal instability.
A research program was initiated to provide key microscopic information about the field surrounding ellipsoidal particles and gain a better insight into granular media under earthquake conditions. Numerical studies of steady streaming... more
A research program was initiated to provide key microscopic information about the field surrounding ellipsoidal particles and gain a better insight into granular media under earthquake conditions. Numerical studies of steady streaming flows are presented for spheroidal particles oscillating in a viscous fluid. Several aspect ratios and angular positions of the spheroids were studied with respect to the Reynolds number. The results were compared with the published experimental data of Kotas et al. (2006). Additional simulations were performed to verify the predicted value of the drag force acting on ellipsoids in creeping, laminar, and separated flows. Results of the simulations were compared with a correlation formula based on a large volume of experimental data published by Hölzer and Sommerfeld (2008). A discussion on the use of ellipsoidal particles for computer simulations of soil behavior at the micro scale concludes the article. RÉSUMÉ Un programme de recherche a été établi po...
The shear modulus and hysteretic damping of three sensitive clays from the sediments of Champlain Sea were investigated using a combined triaxial simple shear apparatus. The tests were conducted on undisturbed samples and were carried out... more
The shear modulus and hysteretic damping of three sensitive clays from the sediments of Champlain Sea were investigated using a combined triaxial simple shear apparatus. The tests were conducted on undisturbed samples and were carried out on a wide range of shear strains from about 0.001% to 1%. The values of the small-strain shear modulus of the tested clays were further confirmed through a series of piezoelectric ring actuator tests. Although the shear modulus and damping ratio of the sensitive eastern Canadian clays follow some classic literature models, the results show that the examined clays exhibited more linear behaviour. Such behaviour may be attributed to their highly structured nature compared to other clays. The compilation of available data on the shear modulus and damping ratio of several sensitive eastern Canadian clays confirmed this trend and showed that some literature models might not be representative.
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Owing to the lack of complementary shear stress on vertical boundaries of a direct simple shear (DSS) specimen, the stress/strain distributions in soil specimens are not uniform. Although the previous studies discussed the effect of... more
Owing to the lack of complementary shear stress on vertical boundaries of a direct simple shear (DSS) specimen, the stress/strain distributions in soil specimens are not uniform. Although the previous studies discussed the effect of diameter-to-height ratio (D/H) on the mechanical and dynamic properties of soil, there is a lack of experimental studies that cover the influence of D/H ratio on the liquefaction potential of sand under stress and strain-controlled conditions. In this study, the influence of the D/H ratio on the cyclic behaviour and liquefaction potential of Ottawa sand C-109 and Ottawa sand F-65 specimens is experimentally investigated. Reconstituted soil specimens of Ottawa sands were prepared at four different D/H ratios using the combined triaxial simple shear (TxSS) and conventional DSS devices. The influence of the D/H ratio on the cyclic behaviour in terms of pore pressure generation and decay of the cyclic stress ratio is emphasized and implicitly discussed with the aid of the energy concept. The stress distribution inside the specimen was deduced and demonstrated by numerical simulation of the TxSS test using a pre-calibrated coupled energy-based pore pressure model. The results indicate that the soil specimens with a D/H ratio greater than 2.5 induce comparable liquefaction potential irrespective of the D/H ratio.
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While cyclic triaxial (CTX) tests are widely used in liquefaction studies due to their simplicity, direct simple shear (DSS) tests and their ilk (e.g., the combined triaxial simple shear, TxSS) are more representative of stress conditions... more
While cyclic triaxial (CTX) tests are widely used in liquefaction studies due to their simplicity, direct simple shear (DSS) tests and their ilk (e.g., the combined triaxial simple shear, TxSS) are more representative of stress conditions produced during an earthquake. Therefore, the CTX results should be properly correlated to simulate field conditions. In the current study, a series of CTX testing results performed on reconstituted samples of Baie-Saint-Paul, Ottawa C-109, and Quebec CF6B sands are compared to the corresponding TxSS and DSS results under both stress- and strain-controlled conditions. The cyclic TxSS stress-controlled tests are numerically simulated by adopting a coupled energy-based pore water pressure model using the computer code, FLAC. The TxSS numerical results are successfully compared with those obtained experimentally from (1) alternative stress-controlled TxSS, (2) available liquefaction potential curves (CSR-Nliq) in the literature, and (3) stress-controlled DSS testing results. As anticipated, the outcomes of the cyclic stress-controlled CTX testing results in the form of liquefaction potential curves are usually higher than that of the TxSS testing results. In contrast, due to the difference in the applied (strain-controlled tests) and the induced (stress-controlled tests) strains, the liquefaction resistance curves of TxSS are higher than those of CTX under cyclic strain-controlled test.
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The establishment of relationships between the shear wave velocity (Vs) and other geotechnical parameters of rockfills under large strains (e.g., oedometer-constrained modulus, Moedo, and tangent elastic modulus, Et) is a significant step... more
The establishment of relationships between the shear wave velocity (Vs) and other geotechnical parameters of rockfills under large strains (e.g., oedometer-constrained modulus, Moedo, and tangent elastic modulus, Et) is a significant step toward precise modeling of earth structure stress–strain behavior. In this study, four specimens reconstituted from the rockfill used for Romaine-2 dam construction were investigated experimentally to correlate small-strain to large-strain moduli. The development of Moedo and Vs with consolidation was measured in a laboratory using the piezoelectric ring-actuator technique (P-RAT) incorporated in a large oedometer cell. A correlation between Moedo and the small-strain shear modulus (Go) was proposed. Moreover, numerical simulations were performed using the Duncan–Chang hyperbolic model to correlate Vs and the Duncan–Chang initial elastic modulus (Ei), which depends on the minor principal stress (σ3). Based on the experimental and numerical data, a ...
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Abstract Buoyancy is one of the most serious manifestations of underground structure’s instability during strong ground motions. Soil liquefaction along with significant reduction of its shear modulus beneath these structures are the main... more
Abstract Buoyancy is one of the most serious manifestations of underground structure’s instability during strong ground motions. Soil liquefaction along with significant reduction of its shear modulus beneath these structures are the main driving factors of this phenomenon. In this article, the seismic behavior of underground access structures embedded in sandy deposits was analyzed using the finite differences (FD) program (FLAC) with an emphasis on structural failures under real earthquakes. A new liquefaction model “energy-based approach” which simulates material cyclic behavior and estimates pore water pressure build-up, was incorporated into the numerical code as a constitutive model of the soil. Also, linear structural elements were used to model the underground structure. Several mitigation methods have been modelled against the structure flotation. As well as a new combined mitigation method and its impacts on the structural performance have been detailed herein. Numerical results showed that gravel drains would effectively dissipate the excess pore water pressure beneath the structure while increasing the burial depth of the structure and adding an impermeable layer under it would increase the vertical effective stress and therefore detracts the ability of excess pore water pressure to push the structure upward. It is found that compiling a gravel drains surround the structure with an impermeable layer beneath the structure would effectively reduce the structural uplift more than any other stand-alone method.
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The demand for a precise evaluation of shear wave velocity Vs, is gaining interest in the field of geotechnical engineering due to its importance as a key parameter required to properly evaluate typical characteristics of soils. Nowadays,... more
The demand for a precise evaluation of shear wave velocity Vs, is gaining interest in the field of geotechnical engineering due to its importance as a key parameter required to properly evaluate typical characteristics of soils. Nowadays, Vs measurements are performed on the field using different methods, such as SCPT tests and various geophysical methods. However, the effectiveness of these field measurements is not guaranteed and rather depends on how they are analyzed. Furthermore, a proper analysis is critical since the collected data may be used in liquefaction evaluation or earthquake ground response analyses. In these situations, it is recommended to verify the coherence between the obtained geophysical (Vs) and geotechnical (N-SPT, qc-CPT) measurements using alternative methods (e.g., Vs-correlations, H/V method, etc...). In some situations, the correlation between the different measurements makes it easier to unambiguously define seismic wave profiles. In other cases, geoph...
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This paper presents a combined triaxial simple shear (TxSS) apparatus developed by the Research Institute of Hydro-Québec (IREQ) in collaboration with the soil dynamics and geotechnical engineering group of the Université de Sherbrooke... more
This paper presents a combined triaxial simple shear (TxSS) apparatus developed by the Research Institute of Hydro-Québec (IREQ) in collaboration with the soil dynamics and geotechnical engineering group of the Université de Sherbrooke (Québec, Canada). The TxSS system consists of a simple shear apparatus incorporated in a triaxial cell for the measurements of monotonic and dynamic characteristics of soil samples. A general description as well as some applications and advantages of the TxSS systems over the traditional apparatus are presented. The key application of the TxSS is the evaluation of liquefaction potential of soil under regular or irregular excitations. Test results in terms of monotonic and dynamic characteristics obtained using the TxSS device on different cohesive and cohesionless soil samples are presented to illustrate its capabilities. They are successfully compared to those obtained using reliable design charts available in the literature, conventional apparatus a...
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Stiffness degradation, G/G0, curves of Champlain clay at St-Adelphe, Quebec, and the associated variation of its damping ratio with shear strain are constructed in this study using the new combined triaxial simple shear (TxSS) apparatus.... more
Stiffness degradation, G/G0, curves of Champlain clay at St-Adelphe, Quebec, and the associated variation of its damping ratio with shear strain are constructed in this study using the new combined triaxial simple shear (TxSS) apparatus. The apparatus offers the ability to obtain the stiffness (G/G0) and damping ratio of soils over a wide strain spectrum from 0.001% to 10%. The value of the small-strain stiffness of the tested clay is further confirmed through another series of piezoelectric ring-actuator technique (P-RAT) tests. Although, the stiffness degradation curve of the tested clay follows to some extent traditional curves suggested in the literature, the examined Champlain clay exhibits a different trend with respect to hysteresis damping, especially at large strains (>1%), and available analytical models could not successfully predict the damping behavior of the Champlain clay at such a strain level. A new constitutive model is therefore presented as a modification of t...
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This article reports a modified setup for an automatic oedometer apparatus that was designed at the Universite de Sherbrooke, Quebec, Canada. The proposed setup can be used to simultaneously measure the superimposed volume change of a... more
This article reports a modified setup for an automatic oedometer apparatus that was designed at the Universite de Sherbrooke, Quebec, Canada. The proposed setup can be used to simultaneously measure the superimposed volume change of a soil specimen caused by mechanical loading and suction imposition along with continuous measurement of water exchange. The combined use of air and water volume/pressure controllers allows the operator to use the axis translation technique to impose matric suction. The setup can also be used to carry out the conventional negative water column technique using a single burette or the water volume/pressure controller to apply suction within the range of 0 kPa to 25 kPa under atmospheric air pressure conditions. A modified Tempe cell was designed to ensure the airtightness of the cell and enhance the freedom of the specimens to move vertically during one-dimensional loading and soil-water retention tests, which is particularly of interest for practical cases in which accurate vertical deformation measurement (as low as 0.02 %) is required. Details of the calibration and test procedures are described and discussed. The test results of reconstituted specimens of a fine sand mixture and Ascot Corner silt are also presented to demonstrate the key features of the modified apparatus.
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The most widely used methods for the in situ investigation of the mechanical characteristics of soil are field penetration tests such as the standard and cone penetration tests, which apply several empirical correlations. Many... more
The most widely used methods for the in situ investigation of the mechanical characteristics of soil are field penetration tests such as the standard and cone penetration tests, which apply several empirical correlations. Many geotechnical researchers have tried to improve the empirical correlations by analyzing comparisons of field penetration tests and laboratory simulations, as well as virtual numerical simulations. However, geotechnical parameters such as relative density, void ratio range, grain size distribution, angularity, mean particle size, uniformity coefficient, effective overburden stress, and mean confinement stress have interlocking effects. Consequently, the use of calibration chambers, which can simulate ideal conditions for the soil in the laboratory, are essential. The authors have developed an axisymmetric innovative simulator system, not only to perform parametric studies on the aforementioned parameters but also to simulate a range of field conditions under substantially controlled boundary conditions. This article also presents results for a series of calibration tests to prove its applicability on nonplastic silts, sands, and granular materials. Repetitive tests, under identical testing circumstances, verified the accuracy, efficiency, and durability of the system. The current work also correlates with the results of comparative studies to investigate the effectiveness of the simulations.
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Upon close scrutiny of data reported in the literature, taking into account particle-scale characteristics to optimize the precision of the well-known empirical Bolton’s equations and imposing particle-size limits on them is recommended.... more
Upon close scrutiny of data reported in the literature, taking into account particle-scale characteristics to optimize the precision of the well-known empirical Bolton’s equations and imposing particle-size limits on them is recommended. The present paper examines the potential influence of particle size and grading on the shear strength–dilation relation of granular materials from the results of 276 symmetrical direct shear tests. The applicability of physical symmetrical direct shear tests to interpret the plane strain frictional shearing resistance of granular materials has been widely discussed using the discrete element method (DEM) computer code SiGran. Sixteen different grain-size distribution curves of three different materials were tested at different normal pressures and initial relative densities. It is demonstrated that while the contribution of dilatancy to shear strength is not influenced by the variation in the coefficient of uniformity, Cu, in the investigated range,...