Showing papers in "International Journal of Geomechanics in 2015"
TL;DR: In this paper, a new constitutive model for cyclic loading of soil to predict the behavior of soft clays under undrained cyclic triaxial loading is presented, inspired by the modified Cam-clay theory.
Abstract: This paper presents a new constitutive model for cyclic loading of soil to predict the behavior of soft clays under undrained cyclic triaxial loading. It is inspired by the modified Cam-clay theory, and a new yield surface for elastic unloading is proposed to capture the soil behavior under cyclic loading. Only two additional parameters that characterize the cyclic behavior are used together with the traditional parameters associated with the modified Cam-clay constitutive model. The details of the relevant soil properties, initial states, and cyclic loading conditions are presented, and a computational procedure for determining the effective stresses and strains is demonstrated. The new model is used to simulate cyclic triaxial tests on kaolin, and the model predictions are generally found to be in agreement with the measured excess pore pressures and axial strains. Furthermore, numerous factors that influence the cyclic performance of soft soils can be considered in the new model, such as cyclic...
76 citations
TL;DR: In this paper, a series of fully coupled three-dimensional thermomechanical finite-element analyses has been carried out to investigate the mechanical and thermal interaction effects induced in a small piled raft equipped with energy piles during the operation of an air-conditioning system based on ground source heat pumps (GSHPs).
Abstract: In this work, a series of fully coupled three-dimensional thermomechanical finite-element analyses has been carried out to investigate the mechanical and thermal interaction effects induced in a small piled raft equipped with energy piles during the operation of an air-conditioning system based on ground source heat pumps (GSHPs). In particular, attention has focused on (1) the axial-load redistribution among the various piles of the raft as a result of differential thermal dilations occurring in the pile and the soil during the transient heat conduction process and (2) the thermal interaction effects that may affect the heat exchange process when multiple energy piles are placed at short distances within the same piled raft. The results of the numerical simulations, which are in qualitative agreement with the limited experimental observations from full-scale tests on energy piles currently available in the literature, show that significant (positive and negative) axial-load changes can be experie...
73 citations
TL;DR: In this paper, the effects of the seismic soil-pile-structure interaction (SSPSI) on the dynamic response of buildings with various heights by conducting a series of shaking table tests on 5-, 10-and 15-story model structures are investigated.
Abstract: The present research intends to study the effects of the seismic soil-pile-structure interaction (SSPSI) on the dynamic response of buildings with various heights by conducting a series of shaking table tests on 5-, 10-story, and 15-story model structures. Two types of foundations for each case are investigated, including (1) a fixed-base structure, representing the situation excluding the soil-structure interaction; and (2) a structure supported by an end-bearing pile foundation in soft soil. An advanced laminar soil container has been designed that uses three-dimensional numerical modeling to minimize the boundary effects and to simulate free-field motion during the shaking table tests. Four real earthquake events, including Kobe 1995, Northridge 1994, El Centro 1940, and Hachinohe 1968, are imposed to each model. According to the experimental measurements, it is observed that the SSPSI amplifies the maximum lateral deflections and in turn interstory drifts of the structures supported by end-bea...
67 citations
TL;DR: In this article, an analytical solution is presented to predict deformation behaviors of geotextile-encased stone columns at any depth below the top plane of the columns, based on the unit-cell concept.
Abstract: Based on the unit-cell concept, analytical solutions are presented to predict deformation behaviors of geotextile-encased stone columns at any depth below the top plane of the columns. Under vertical loads at the tops of the stone columns, an axial compression deformation occurs that is often accompanied by a lateral expansion near the top. This deformation characteristic of stone columns was incorporated directly into the proposed analytical method. The shear stress between the encased stone column and the surrounding soil in the vertical direction also was taken into account. In this method, the confining pressure provided by the soil was analyzed based on an analogy with passive earth pressure. The method was verified via comparison with two other analytical solutions. Parametric studies were conducted to investigate the effects of geotextile encasement, vertical applied stress, and column spacing and diameter on the deformation behaviors of columns. The results indicated that geotextile encase...
60 citations
TL;DR: In this article, a simple nonlinear creep formulation is proposed accounting for the effect of volumetric packing of soil assemblies, which is then incorporated into a newly developed elastic-viscoplastic model to take into account the non-linear creep of natural soft clays.
Abstract: This paper focuses on nonlinear creep behavior with a consecutively decreasing creep coefficient Cαe fully related to the soil density. Conventional oedometer tests on reconstituted samples of several natural soft clays are selected to clarify the evolution of creep coefficient throughout testing. On this basis, a simple nonlinear creep formulation is proposed accounting for the effect of volumetric packing of soil assemblies. The formulation is then incorporated into a newly developed elastic-viscoplastic model to take into account the nonlinear creep of natural soft clays. One additional parameter is added that can be determined in a straightforward way from an oedometer test without additional experimental cost. The enhanced nonlinear creep model is examined by simulating a conventional oedometer test on reconstituted Haarajoki clay. The improvement of predictions by the nonlinear creep formulation is highlighted by comparing predictions with constant Cαe. The enhanced model is further applied ...
58 citations
TL;DR: In this paper, the authors used finite-element upper and lower bound limit analysis to assess the short-term stability of slopes in which the slope material and subgrade foundation material have two distinctly different undrained strengths.
Abstract: Stability charts for soil slopes, first produced in the first half of the twentieth century, continue to be used extensively as design tools, and draw the attention of many investigators. This paper uses finite-element upper and lower bound limit analysis to assess the short-term stability of slopes in which the slope material and subgrade foundation material have two distinctly different undrained strengths. The stability charts are proposed, and the exact theoretical solutions are bracketed to within 4.2% or better. In addition, results from the limit-equilibrium method (LEM) have been used for comparison. Differences of up to 20% were found between the numerical limit analysis and LEM solutions. It also shown that the LEM sometimes leads to errors, although it is widely used in practice for slope stability assessments.
58 citations
TL;DR: In this paper, a 3D numerical investigation of axisymmetric collapse of granular columns has been conducted using the discrete element method (DEM), where rotational velocities of particles are reduced by a factor at every time step to partially account for the additional rolling resistance due to the effect of particle shape and hysteretic contact behavior.
Abstract: In this study, a three-dimensional (3D) numerical investigation of axisymmetric collapse of granular columns has been conducted using the discrete element method (DEM). The simulated granular columns have a constant initial radius of 5.68 mm and three aspect ratios: 0.55, 1.0, and 2.0. The columns consist of uniform spherical quartz particles with a diameter of 0.32 mm. In the DEM model, rotational velocities of particles are reduced by a factor at every time step to partially account for the additional rolling resistance due to the effect of particle shape and hysteretic contact behavior. The simple linear contact model is used; however, its performance is improved by using different stiffness values calculated by nonlinear Hertz–Mindlin contact model for each aspect ratio. The simulated final deposit heights, runout distances, and energy dissipation values are in good agreement with experimental observations reported in the literature. The effects of initial porosity and rotational resistance on...
56 citations
TL;DR: In this paper, the results and lessons learned using a FEM model to simulate quantitative performance features of the Minnow Creek steel-strip reinforced soil wall structure located in the United States are described.
Abstract: The paper describes the results and lessons learned using a FEM model to simulate quantitative performance features of the Minnow Creek steel-strip reinforced soil wall structure located in the United States. The Minnow Creek Wall structure was constructed and instrumented in 1999. It is a unique case study because of the comprehensive measurements that were taken to record a wide range of wall performance features. Two different constitutive models for the soil were used (a linear-elastic Mohr-Coulomb model and hardening soil model with a Mohr-Coulomb failure criterion), and numerical outcomes were compared with physical measurements. The numerical results were shown to be sensitive to boundary conditions assumed at the toe of the wall. The generally encouraging agreement between physical and numerically predicted results gives confidence that commercial FEM software packages can be useful for the analysis and design of these types of structures, provided that care is taken in the selection of in...
56 citations
TL;DR: In this article, a constitutive model based on the Mohr-Coulomb model is presented for the simulations of strain-softening behavior of cement-mixed clays.
Abstract: Geotextile-reinforced embankments over deep cement mixed (DCM) columns are widely used for the construction of highway embankments over soft clay with low shear strength and high compressibility. Numerical modeling based on the finite element method (FEM) is widely used to investigate the behavior of these embankments during construction and serviceability, incorporating consolidation of the foundation soil over time. However, not much attention has been paid to the strain-softening behavior of DCM columns beyond yield, which is essential in ultimate limit-state computations to determine the stability of embankments during the failure of columns. This paper presents a constitutive model, which is an extension of the Mohr-Coulomb model, for the simulations of strain-softening behavior of cement admixed clays. The model is validated using triaxial test data found in the literature for cement admixed Singapore and Hong Kong marine clays and Ariake clay. A two-dimensional (2D) coupled mechanical and hydraulic numerical implementation of a geotextile-reinforced DCM column-supported (GRCS) embankment constructed over a very soft soil in Finland is carried out incorporating strain-softening behavior of DCM columns. Even though the isolated columns and overlapped column walls used in this embankment do not yield significantly under the service loads, the model simulations show good agreement with field data, confirming the capability of the 2D plane strain finite-element model in predicting the GRCS embankment behavior. Finally, the finite-element model with strain-softening DCM columns is used to investigate the progressive failure of a typical hypothetical GRCS embankment with isolated columns in a square pattern. Results clearly illustrate the bending failure mode caused by progressive softening of the DCM columns, including the plastic hinge development within the columns.
55 citations
TL;DR: In this paper, a series of large-scale triaxial compression tests on Tacheng rockfill material (TRM) showed that the dilatancy and stress-strain behaviors were significantly influenced by density and pressure.
Abstract: A series of large-scale triaxial compression tests on Tacheng rockfill material (TRM) showed that the dilatancy and stress-strain behaviors were significantly influenced by density and pressure. The critical state friction angle of TRM decreased with an increase in the initial confining pressure. In addition, the critical state line of this material in the e-logp′ plane ascended with an increase in the initial void ratio. On the basis of the specific critical state behaviors of TRM, a state-dependent constitutive model was slightly adapted in the triaxial stress space. The model, with only a set of model parameters, could capture the state-dependent behaviors of the dilatancy, stress-strain, and mobilized friction angle of TRM at various densities and pressures. The peak friction angle of TRM was found to be linear, with a coefficient of 0.21, in relation to the maximum dilatancy angle. The coefficient for rockfill materials was smaller than that for sands, indicating that the influence of dilata...
49 citations
TL;DR: In this article, the authors presented an analytical model to predict the bearing capacity of soft soil reinforced with stone columns under rigid raft foundation subject to general shear-failure mechanism.
Abstract: Installation of stone column is a viable, cost effective, and environmentally friendly ground-improvement technique. Columns are made of compacted aggregate and are installed in weak soil as reinforcements to increase the shear resistance of the soil mass and, accordingly, its bearing capacity. While a single stone column mostly fails by bulging, a group of stone columns together with the surrounding soil may fail by general, local, or punching shear mechanism, depending on the soil/columns/geometry of the system. The mode of failure of the reinforced ground could be identified based on the ground geometry and strength parameters of both stone column and soft soil. This paper presents an analytical model to predict the bearing capacity of soft soil reinforced with stone columns under rigid raft foundation subject to general shear-failure mechanism. The model utilizes limit-equilibrium method and the concept of composite properties of reinforced soil. The proposed theory was validated for the case of bearing capacity of footings on homogenous soil and via the laboratory and numerical results available in the literature for this case. Design procedure and charts are presented for practicing purposes.
TL;DR: In this paper, the effect of particle shape and particle crushing on the results of cone penetration testing (CPT) of granular materials in a calibration chamber has been studied using three-dimensional discrete element modeling.
Abstract: The effect of particle shape and particle crushing on the results of cone penetration testing (CPT) of granular materials in a calibration chamber has been studied using three-dimensional discrete element modeling. Simulating the whole chamber with a realistic particle size requires a large number of particles, which leads to a large computational time. Both 90° and 30° segments of a calibration chamber were used in this study to reduce computational time. The effect of particle shape was simulated by prohibiting particle rotation or using simple two-ball clumps. Prohibiting particle rotation was found to increase tip resistance significantly compared with free particle rotation, and replacing a single sphere with different shapes of simple two-ball clumps was also found to have an important effect on the tip resistance. Particle crushing was simulated during CPTs by replacing a broken particle with two new equal-sized smaller particles. The results showed that there was a considerable reduction i...
TL;DR: In this article, the authors present and validate a numerical technique for the simulation of the overtopping and onset of failure in rockfill dams due to mass sliding, which is achieved by coupling a fluid dynamic model for simulation of free surface and through-flow problems, with a numerical techniques for the calculation of the rockfill response and deformation.
Abstract: This paper aims to present and validate a numerical technique for the simulation of the overtopping and onset of failure in rockfill dams due to mass sliding. This goal is achieved by coupling a fluid dynamic model for the simulation of the free surface and through-flow problems, with a numerical technique for the calculation of the rockfill response and deformation. Both the flow within the dam body and in its surroundings are taken into account. An extensive validation of the resulting computational method is performed by solving several failure problems on physical models of rockfill dams for which experimental results have been obtained by the authors.
TL;DR: In this article, a fully analytical solution is proposed for analysis of underwater cavities excavated in elastic-brittle-plastic and Mohr-Coulomb rock material, considering the induced seepage forces under steady-state flow.
Abstract: In a drained underwater cavity, seepage forces and pore-water pressure that develop around the cavity may affect the response of the rock mass. In this paper, a fully analytical solution is proposed for analysis of underwater cavities excavated in elastic–brittle–plastic and Mohr-Coulomb rock material, considering the induced seepage forces under steady-state flow. The initial stress state is assumed to be hydrostatic, and the seepage flow is assumed to be radial; thus, the problem is considered axisymmetric. In the proposed solution, in contrast to the failure processes that are represented as a function of Terzaghi’s effective stresses, the induced deformations are considered as a function of Biot’s effective stresses. The proposed solution is used to explain the behavior of cavities under different hydromechanical conditions. The results show that, in the case of drained cavities, seepage flow causes the induced radial displacements to increase and the stability of the cavity to decrease. From ...
TL;DR: In this article, the bearing capacity factors of a shallow embedded horizontal strip footing placed on a sloping ground surface were determined by using the lower bound theorem of the limit analysis in conjunction with finite elements and nonlinear optimization.
Abstract: By using the lower-bound theorem of the limit analysis in conjunction with finite elements and nonlinear optimization, bearing-capacity factors, N-c and N-gamma q, with an inclusion of pseudostatic horizontal seismic body forces, have been determined for a shallow embedded horizontal strip footing placed on sloping ground surface. The variation of N-c and N-gamma q with changes in slope angle (beta) for different values of seismic acceleration coefficient (k(h)) has been obtained. The analysis reveals that irrespective of ground inclination and the embedment depth of the footing, the factors N-c and N-gamma q decrease quite considerably with an increase in k(h). As compared with N-c, the factor N-gamma q is affected more extensively with changes in k(h) and beta. Unlike most of the results reported in literature for the seismic case, the present computational results take into account the shear resistance of soil mass above the footing level. An increase in the depth of the embedment leads to an increase in the magnitudes of both N-c and N-gamma q. (C) 2014 American Society of Civil Engineers.
TL;DR: In this paper, the authors investigated the behavior of soil arching under dynamic load in pile-supported, geosynthetic-reinforced or unreinforced embankments resting on soft soil.
Abstract: Soil arching is a common phenomenon in pile-supported, geosynthetic-reinforced or unreinforced embankments resting on soft soil. Although the system behavior under static loading is well known (soil arching and bearing effects in geosynthetic reinforcement), the bearing behavior under dynamic loading is not yet fully understood and cannot be predicted. In this paper, the properties of soil arching under dynamic load have been investigated by performing numerical studies using the FEM and model tests. Embankments with different heights under dynamic load have been investigated. The behavior of soil arching under dynamic load can be classified into two types: for the model test without a geogrid and subsoil, the soil arching collapsed under dynamic load when the ratio of the height of the embankment to the diameter of the hole is less than 3, whereas the soil arching will not collapse under dynamic load when the ratio of the height of the embankment to the diameter of the hole is greater than 3. In ...
TL;DR: In this article, a semianalytical solution using the power series method was proposed to assess the behavior of a vertical pile with variable cross sections and embedded in a multilayered soil system to support lateral loads at its head.
Abstract: Piles have been widely used to resist lateral loads in geotechnical engineering. In reality, piles are always embedded in layered soils; however, theoretical solutions for laterally loaded piles in multilayered soil system are limited in the literature. Based on the basic concept of the subgrade reaction theory, semianalytical solutions using the power series method were proposed to assess the behavior of a vertical pile with variable cross sections and embedded in a multilayered soil system to support lateral loads at its head. For the present method, the moduli of the lateral subgrade reaction were assumed to be of constant depth for clay soil and of linearly increasing depth for sandy soil. By considering the deflection and force continuum conditions along the pile length, a matrix form of pile response at any depth was expressed through the deflections and lateral forces at the pile head. The validity of the presented solution was verified by back-predicting behaviors of laterally loaded piles...
TL;DR: In this article, a coupled framework that takes advantage of both the finite and discrete-element approaches to investigate soil-geogrid interactions is described, where finite elements are used to model the structural components and discrete particles are modeled the surrounding soil to reflect the discontinuous nature of the granular material.
Abstract: Three-dimensional analysis of soil-structure interaction problems considering the response at the particle scale level is a challenging numerical modeling problem. An efficient framework that takes advantage of both the finite- and discrete-element approaches to investigate soil-geogrid interactions is described in this paper. The method uses finite elements to model the structural components and discrete particles to model the surrounding soil to reflect the discontinuous nature of the granular material. The coupled framework is used in this study to investigate two geotechnical engineering problems, namely, strip footing over geogrid-reinforced sand and geogrid-reinforced fill over a strong formation containing void. The numerical model is first validated using experimental data and then used to provide new insights into the nature of the three-dimensional interaction between the soil and the geogrid layer.
TL;DR: In this paper, the performance of geosynthetic reinforced piled embankment systems (GRPESs) from three modeling approaches [axisymmetric, three-dimensional (3D) column, and full 3D models] were compared.
Abstract: Geosynthetic reinforced piled embankment systems (GRPESs) have proven to be an effective and economical technique to address the problems posed during the construction of embankments on soft soils. In this paper, the predictions of the performance of GRPESs from three modeling approaches [axisymmetric, three-dimensional (3D) column, and full 3D models] were compared. The numerical models in this study were calibrated against the measured data of GRPESs from a full-scale field test. The load distribution between different components of the GRPES and the tensile force developed in the geosynthetic reinforcement were compared with the results obtained using various design methods and other analytical results. Further, the numerical investigation was extended to examine the tensile force developed among the layers of a multilayer GRPES, and the results were compared with the empirical solutions.
TL;DR: In this article, a cyclic elastoviscoplastic constitutive model for clayey soils is proposed based on the nonlinear kinematic hardening rules and considering the structural degradation.
Abstract: A cyclic elastoviscoplastic constitutive model for clayey soils is proposed based on the nonlinear kinematic hardening rules and considering the structural degradation. The performance of the model is verified through the undrained triaxial test simulation of soft clay samples under cyclic and monotonic loading conditions and the cyclic compression test. The simulated results are compared with the experimental data through stress-strain relations and stress paths. The simulated results have shown a good agreement with the experimental data, which indicates the capability of the proposed model to reproduce the cyclic behavior of soft clayey soils.
TL;DR: In this article, the authors investigated the application of high-order elements within the framework of the arbitrary Lagrangian-Eulerian method for the analysis of elastoplastic problems involving large deformations.
Abstract: This paper investigates the application of high-order elements within the framework of the arbitrary Lagrangian-Eulerian method for the analysis of elastoplastic problems involving large deformations. The governing equations of the method as well as its important aspects such as the nodal stress recovery and the remapping of state variables are discussed. The efficiency and accuracy of 6-, 10-, 15-, and 21-noded triangular elements are compared for the analysis of two geotechnical engineering problems, namely, the behavior of an undrained layer of soil under a strip footing subjected to large deformations and the soil behavior in a biaxial test. The use of high-order elements is shown to increase the accuracy of the numerical results and to significantly decrease the computational time required to achieve a specific level of accuracy. For problems considered in this study, the 21-noded elements outperform other triangular elements.
TL;DR: In this paper, a series of direct shear box tests are conducted on a compacted completely decomposed granite (CDG) soil-grout interface in a cast in situ condition under different matric suctions and net normal stresses.
Abstract: The dilatancy of a soil is significantly influenced by matric suction, and it affects the apparent friction angle and shear strength of the soil. To examine the influence of dilatancy on interface behavior, a series of direct shear box tests are conducted on a compacted completely decomposed granite (CDG) soil–grout interface in a cast in situ condition under different matric suctions and net normal stresses. The test results indicate that matric suction and net normal stress have significant influence on the hardening-softening and dilatancy of the soil–cement grout interface. The failure envelopes for different matric suctions are observed as linear. The apparent interface friction angle and adhesion intercept increase with matric suction. The suction envelope is found to be nonlinear as the δb-angle decreases with matric suction. A modified model is proposed to consider the influence of dilatancy on the apparent interface friction angle and hence on the interface shear strength. Experimental sh...
TL;DR: In this paper, the stability condition of a tunnel face excavated by an earth pressure balanced shield (EPBS) in Line 3 of the Tehran subway in Iran was investigated, and data simulation by Monte Carlo technique was applied.
Abstract: The stability condition of the tunnel face is of great importance in both conventional and modern [tunnel-boring machine (TBM)] methods of construction. Inadequate and excessive amounts of support pressure toward the face lead to surface settlement and blowout, respectively, whereas blowout occurs only in cases of pressurized shield implementation. In this research, the stability condition of a tunnel face excavated by an earth pressure balanced shield (EPBS) in Line 3 of the Tehran subway in Iran was investigated. Considering the sensitivity of urban facilities to ground movement, and to reduce uncertainty, data simulation by Monte Carlo technique was applied. Random data generated through a simulation process were used in an analytical method to calculate the factor of safety and its probability of being less than a predetermined value for a certain amount of applied support pressure. The soil was modeled by finite-element software, and the amount of face pressure at which the face collapses was...
TL;DR: In this article, the failure probability of a cantilever sheet pile wall is combined with the sensitivity of geotechnical random variables on the failure mode, and a new factor, the probabilistic risk factor (Rf), is proposed for each random variable corresponding to different variations of the random variables.
Abstract: The paper presents an analytical study of a cantilever sheet pile wall considering the effects of uncertainty of soil properties. The failure probability (Pf) of the sheet pile wall is combined with the sensitivity (S) of geotechnical random variables on the failure mode, and a new factor, the probabilistic risk factor (Rf), is proposed for each random variable corresponding to different variations of the random variables. The cantilever sheet pile wall that is driven into a cohesionless soil layer and backfilled by (1) cohesionless soil and (2) cohesive soil is considered separately for analysis against the rotational failure mode. Pf is obtained by developing the response surface, based on finite element models. The sensitivity of each random variable is obtained by F-test analysis. It is observed that the cohesion of foundation soil (c2) and water table positions are the important factors that influence the stability of the cantilever sheet pile walls to a great extent. Finally, design guidelin...
TL;DR: Wang et al. as mentioned in this paper investigated the stress dilatancy of natural soft clay during an undrained creep and obtained a unique stress-dilatancy curve from all test results.
Abstract: The stress–dilatancy relationship is a key point to capture the evolution of both strains and excess pore pressure during an undrained
creep of natural soft clay. This paper focuses on investigating the stress dilatancy of natural soft clay during an undrained creep. Undrained
triaxial creep tests are performed on K0-consolidated and isotropically consolidated samples of a typical Chinese soft marine clay with different
stress levels. A unique stress–dilatancy curve is obtained from all test results. Several typical stress–dilatancy relations for soils are discussed,
comparing them with experimental results. A common modification method for the stress dilatancy of sand is adopted and discussed for clay. All
comparisons demonstrate that modified dilatancy equations can describe the stress–dilatancy relationship during an undrained creep. The
modified dilatancy equation with the inclination of a potential surface seems to better describe the whole trend, and is suitable for natural soft clay.
TL;DR: In this paper, a nonlinear power-type failure envelopes of the form τ=(a+bσ)n were examined and the principal stress σ1-σ3 relations corresponding to these laws were derived explicitly for the quadratic law (n = 1/2) and implicitly for n=1/3, 2/3 and 3/4.
Abstract: Nonlinear power-type failure envelopes of the form τ=(a+bσ)n were examined in this paper. It is shown that equations for which 0
TL;DR: In this article, the authors studied the swelling behavior of sodium (Na)-montmorillonite clays with increasing amounts of hydration using molecular dynamics and showed the important role of bound water and clay-Na interactions during swelling to stabilize clay structure during hydration.
Abstract: In this work, the swelling behavior of sodium (Na)-montmorillonite clay with increasing amounts of hydration is studied using molecular dynamics. The molecular models of the dry clay and the hydrated clays, consisting of 2, 4, 6, 8, and 10 monolayers of water in the interlayer, are used in this study. This work captures the evolution of interaction energies in the interlayer of Na-montmorillonite swelling clay with increasing hydration and provides insight into swelling mechanisms. This work shows the important role of bound water and clay-Na interactions during swelling to stabilize clay structure during hydration. Changes to water molecule conformations in the interlayer during swelling are also reported. The results and insight provided by this work will help in modeling and predicting exfoliation and resulting particle breakdown in swelling clays, in addition to expounding the key role of interlayer interactions on swelling in smectite clays.
TL;DR: In this article, a simplified solution procedure is proposed for estimating the dynamic response of a pile group partially embedded in a layered saturated soil and subjected to horizontal harmonic loading, based on the dynamic interaction factor, the horizontal impedance of the pile group is obtained by using the superposition principle.
Abstract: A simplified solution procedure is proposed for estimating the dynamic response of a pile group partially embedded in a layered saturated soil and subjected to horizontal harmonic loading. In the proposed procedure, the transfer matrix method is first applied to solve the vibration equation of a single pile, from which the stiffness of the single pile is obtained. The existing lateral displacement of the saturated half-space is introduced to build the attenuation function, and the balance equation of passive pile is built accordingly. The simple Winkler model is used to derive the dynamic pile-soil-pile interaction factor. Based on the dynamic interaction factor, the horizontal impedance of the pile group is obtained by using the superposition principle. The calculated dynamic interaction factor and impedance of the pile group are in agreement with earlier results for an idealized case, verifying the correctness of the proposed method. The main parameters, such as the embedment ratio, pile separat...
TL;DR: In this article, a randomly distributed pore network model is first calibrated using experimental data corresponding to the main drying branch of the soil-water retention curve (SWRC), and the influence of the stress state on the pore-size distribution of the network is further studied.
Abstract: The soil-water retention curve (SWRC) is the relationship between the suction values and water content of the soil. This curve has one or more branches depending on the suction imposition paths, and represents one of the most important properties of unsaturated soils. In this paper, by using a percolation approach and introducing a trial-and-error process, a randomly distributed pore network model is first calibrated using experimental data corresponding to the main drying branch of the SWRC. The influence of the stress state on the pore-size distribution of the network is further studied. The calibrated network model is used to predict the main wetting and scanning branches of the SWRC. Piston-type and cooperative fillings are used as the two wetting mechanisms. The proposed method facilitates modeling pore networks with large numbers of pores covering a wide range of suction values (full saturation through the residual degree of saturation). The results indicate that with an increase in the appl...
TL;DR: In this article, a thermomechanical constitutive model for predicting the isothermal behavior of saturated clays in different temperatures is presented, based on the general framework of critical state soil mechanics and modified Cam-clay formulation.
Abstract: A thermomechanical constitutive model for predicting the isothermal behavior of saturated clays in different temperatures is presented in this paper. This model is developed based on the general framework of critical state soil mechanics and modified Cam-clay formulation. Most of the characteristics of saturated clays in temperatures lower than water’s boiling temperature have been taken into account. An attempt has been made to use the lowest possible number of extra parameters compared with the original Cam-clay model and to ensure that these new parameters have clear physical interpretations. An important feature in the model is thermal dependency of the critical state line in the deviatoric stress plane. The predictions have been compared with five sets of laboratory data available in the literature.