SOILS AND FOUNDATIONS
Print ISSN : 1341-7452
Volume 45, Issue 4
Displaying 1-14 of 14 articles from this issue
  • PEI J. GUO, DIETER F. E. STOLLE
    2005 Volume 45 Issue 4 Pages 1-12
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    Anisotropic failure criteria for granular materials are formulated, based on micromechanical analysis. The shear resistance is assumed to consist of two components related to fabric anisotropy and interparticle frictional forces. By considering the directional contribution of contact normals, the failure criteria are developed via two approaches : one employs the invariants of stress and fabric tensors; and the other considers the relation between the traction components acting on the critical plane. In the stress invariant approach, however, some microscopic features of granular materials may not be captured due to the utilization of stress invariants. Numerical examples, examining the variation of shear strength of granular materials with different orientations of bedding plane and the degree of anisotropy, compare the proposed approaches with other models in the literature.
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  • S. BHATTACHARYA, M. D. BOLTON, S. P. G. MADABHUSHI
    2005 Volume 45 Issue 4 Pages 13-25
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    The collapse of piled foundations in liquefiable soil has been observed in the majority of recent strong earthquakes. This paper critically reviews the current understanding of pile failure in liquefiable deposits, making reference to modern design codes such as JRA (1996), and taking the well-documented failure of the Showa Bridge in the 1964 Niigata earthquake as an example of what must be avoided. It is shown that the current understanding cannot explain some observations of pile failure. The current method of pile design under earthquake loading is based on a lateral loading mechanism where inertia and drag due to slope movement (lateral spreading) induce bending in the pile, and where axial load effects are ignored. It is demonstrated here, however, that axial loads can be a dominant factor in collapse due to seismic liquefaction, due to the progressive onset of pile buckling when lateral soil resistance is removed. Additional design considerations based on the avoidance of buckling effects are formulated after back analysing fifteen case histories of pile foundation performance during past earthquakes, and verified using dynamic centrifuge modelling. Some practical implications of the omission of axial loads from previous design verifications are highlighted.
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  • JAE-MYUNG LEE, CHARLES D. SHACKELFORD
    2005 Volume 45 Issue 4 Pages 27-41
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    Both prehydrated and non-prehydrated specimens of a geosynthetic clay liner (GCL) are permeated with chemical solutions containing 5, 10, 20, 50, and 100 mM calcium chloride (CaCl2) to determine the concentration dependency of the prehydration effect on the hydraulic conductivity (k) of the GCL. The tests for k are not terminated before chemical equilibrium between the influent and effluent solutions has been established, resulting in testing durations ranging from 14 hrs to 502 days, depending on the CaCl2 concentration and whether or not the specimen was prehydrated. The results are presented in terms of the ratio of k for a non-prehydrated specimen (kNP) relative to k for a separate but identical prehydrated specimen (kP) permeated with the same chemical solution. Prehydration is shown to have little, if any, effect on the hydraulic conductivity of the GCL for specimens permeated with solutions containing from 5 to 50 mM CaCl2 (i.e., 0.5_??_kNP/kP_??_1.1), whereas the effect of prehydration for specimens of the GCL permeated with the 100 mM CaCl2 solution is more significant (i.e., kNP/kP_??_3.0). The results provide evidence that the previously reported prehydration effect is concentration dependent, and may be insignificant when the permeant liquid contains relatively low concentrations of inorganic solutes, i.e., provided permeation is continued until chemical equilibrium is achieved.
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  • CHAMINDA PATHMA KUMARA GALLAGE, IKUO TOWHATA, SATHOSHI NISHIMURA
    2005 Volume 45 Issue 4 Pages 43-60
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    Experiences of past earthquakes show that many structural damages occur due to liquefaction-induced ground deformation. Accordingly, the prediction of liquefaction-induced ground deformation plays a major role in mitigation of damages. Even though numerical methods are developed in three-dimensional way to predict liquefaction-induced deformation, lack of understanding of mechanical properties of liquefied sand makes the prediction unrealistic. Therefore, employing a hollow cylinder torsion shear apparatus, the present study aims to investigate the large deformation of liquefied sand which is tentatively considered to be rate-dependent. Since it is impossible to run experiments on specimens with null effective stress, tests were conducted at very low effective stresses such as 5, 10, and 15 kPa and possibility for extrapolation of data to zero effective stress was attempted in order to study mechanical properties of liquefied sand. In this study, specimens with low effective stress were further sheared by stepwise monotonic axial compression in drained manner and the shear stress was found to be composed of frictional as well as rate-dependent viscous components. The results suggested that viscosity of sand increases with the increase of the mean effective stress. Note that a triaxial extension test and two tests on a special light grain material (Styrofoam) were conducted to investigate viscosity at low effective stress such as 3 to 4 kPa. Noteworthy was that effects of relative density on viscosity were not significant. The test conducted with pore water, pore air, and vacuum revealed that viscosity of liquefied sand was contributed by pore fluid and particle collision during flow. Furthermore, it was suggested that increase in the fines content leads to lower viscosity.
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  • DORIVAL M. PEDROSO, MÁRCIO M. FARIAS, TERUO NAKAI
    2005 Volume 45 Issue 4 Pages 61-77
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    An isotropic hardening elastoplastic model, named subloading tij, has been recently proposed (Nakai and Hinokio, 2004). Three features differentiate subloading tij model from the conventional ones : (a) the use of a modified stress space given by tensor tij; (b) the split of the plastic strain increments in two components and (c) the use of two yield surfaces based on the concept of subloading. These three characteristics greatly improve the prediction capabilities of the model, with respect to those of the well-known Cam-clay model. However, the model formulation and implementation becomes a little more complex. In this paper the basic equations for the evolution of stresses and strains and for the evolution of the internal variables that control the size of the yield surfaces of the model are reformulated in such a way as to resemble those of any conventional elastoplastic model. This facilitates significantly the numerical integration (explicit or implicit) of the corresponding system of differential equations of the model. The present formulation also identifies the physical meaning of each concept and clearly shows where they intervene in the deduction of the elastoplastic constitutive tensors. The model is initially formulated without taking into account the plastic strain increment split, in order to emphasize the effect of adopting the subloading concept. Then the plastic split is considered using a different approach that allows writing the constitutive tensors in a simpler manner. The procedures proposed were successfully tested and all derivatives and algorithms necessary to implement the model are given in the appendices. The authors hope that these procedures make it easier for other researchers to implement and use the model as it is or to use the basic concepts in any other model.
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  • SEBASTIAN LOBO-GUERRERO, LUIS E. VALLEJO
    2005 Volume 45 Issue 4 Pages 79-87
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    Granular materials forming part of natural slopes, embankments, subgrades of foundations and pavement structures are subjected to both static and dynamic loads during their engineering lives. As a result of these loads, particle crushing occurs. The present study focuses on the evolution of crushing in a simulated granular material subjected to different combinations of biaxial stresses. It was found that the Discrete Element Method (DEM) can be used to visualize and understand the evolution of crushing experienced by a granular material under these conditions. Even though DEM does not normally consider particle breakage, it is possible to simulate crushing by replacing one particle that has failed in tension with a combination of many particles of different sizes. The results from the developed simulations indicated that the samples tended to achieve a fractal distribution of particle sizes, although at the end of the simulations these distributions were still being dominated by the size of the original particles. Changes in other properties of the simulated granular material such as the void ratio and the shear strength were also recorded and analyzed. It was found that the internal friction angle decreased as a result of particle crushing.
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  • MITSUTOSHI YOSHIMINE, REIKO KOIKE
    2005 Volume 45 Issue 4 Pages 89-98
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    This study focused on the effects of stratified structure due to segregation of particle size and graded bedding in clean sand deposits on their liquefaction characteristics. A well-graded clean sand was sieved and separated into four components with different ranges of particle size, and then deposited alternatively to create stratified structure in specimens. Undrained triaxial compression tests in monotonic loading conditions and cyclic triaxial loading tests were performed on these stratified samples as well as the uniformly mixed samples of the same sand. It was observed that the liquefaction resistance of the stratified specimens was larger than the uniform specimens. These test results indicate a possibility of underestimation of liquefaction resistance of deposits with laminar structure in situ, if it is evaluated in the laboratory using homogeneously reconstituted samples.
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  • YOSHITSUGU MOMOYA, ETSUO SEKINE, FUMIO TATSUOKA
    2005 Volume 45 Issue 4 Pages 99-118
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    To develop a relevant performance-based design method for railway asphalt roadbed, the resilient and residual deformation characteristics of railway roadbed and subgrade were investigated by means of scale model tests. In the scale model tests, the difference in the mechanism between moving-wheel loading and fixed-point loading were discussed. The deformation characteristics of roadbed and subgrade in the fixed-point loading which apply cyclic vertical load at a fixed point on rails above a certain sleeper was proved to be substantially different from the trend in behaviour when moving a wheel repeatedly on a model rail as in the full scale railway track. Therefore, it was con-cluded that the moving-wheel loading test is necessary to investigate the deformation characteristics of railway roadbed and subgrade. On the other hand, the result of moving-wheel loading test showed that the resilient deformation characteristics do not change even residual deformation caused by repeated loading. A resilient deformation characteristic of asphalt roadbed is an important factor because the fatigue criterion of asphalt concrete is specified in terms of resilient tensile strain. The resilient deformation characteristics of asphalt roadbed, including the maximum resilient tensile strains in the asphalt concrete layer, were simulated well by linear elastic FEM analysis using exact boundary condition and relevant material parameters described in this paper.
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  • NIKOS GEROLYMOS, GEORGE GAZETAS
    2005 Volume 45 Issue 4 Pages 119-132
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    A dynamic nonlinear Winkler spring model, is developed for the seismic response of deep foundations. The model utilizes the phenomenological “BWGG” model (outlined in a companion paper), and it can treat the inelastic response of both the soil and the pile. The nonlinear reaction of the soil is modeled realistically by the BWGG interaction springs and dashpots, with due consideration to effects such as : separation (gapping) of the pile or caisson from the soil, radiation damping, and loss of strength due to pore-water pressure development. The modeling of pile inelasticity is also versatile, and can treat from well-reinforced to poorly-reinforced concrete sections. The necessity for the proposed model arises from the difficulty to predict the large-amplitude dynamic response of piles up to failure. The BWGG-Winkler model is validated through the results of in-situ monotonic and dynamic pile load tests. It is further utilized to study the nonlinear soil-pile interaction under lateral monotonic loading. The results of the model are compared with the venerable Broms (1964) theory for pile lateral capacity
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  • P. DAKOULAS, G. GAZETAS
    2005 Volume 45 Issue 4 Pages 133-147
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    Deformation-based seismic design of gravity quay-walls requires realistic computation of residual deformations. This article presents an effective-stress analysis method, which is based on an elasto-plastic constitutive model formulated into a finite-difference algorithm. The model is applicable to cohesionless soils, for a wide range of relative densities and confining pressures. The formulation is applied first to re-analyze one of the failed caisson-type quay-walls of Rokko Island during the 1995 Kobe (Hyogoken-nambu) earthquake (Case 1). Subsequently, it is applied to analyse three closely related case studies of quay-walls, subjected to the same earthquake excitation, to demonstrate the effects of ground improvement on the wall performance. Case 2 considers a quay-wall in which both the foundation and backfill consist of improved, non-liquefiable soils. Case 3 considers a quay-wall in which the backfill soil remains liquefiable, whereas the foundation soil has been improved. Finally, in Case 4 the foundation soil is liquefiable, and the backfill soil improved. The results are consistent with both field observations and earlier independent computer simulations by Iai et al. 1998 which were based on the finite-element method and a different constitutive model.
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  • RYOSUKE UZUOKA, NORIAKI SENTO, MOTOKI KAZAMA, TOSHIYASU UNNO
    2005 Volume 45 Issue 4 Pages 149-163
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
    We conducted a site investigation for two major landslides : Dateshita landslide, Tsukidate-cho during the earthquake on May 26, 2003; and Nishisaruta landslide, Kanan-cho during the earthquake on July 26, 2003. In addition, we examined physical and mechanical soil properties and performed preliminary numerical simulations. The subsurface soil of the gentle slope of Dateshita landslide with an angle of about 7° was a fill with pyroclastic sediments. The structure of the fill was very loose, but the unsaturated soil remained stable with high suction. The landslide occurred during or immediately after the principle motion of the earthquake. The slide mass behaved as a mudflow. Then the collapsed soil easily fluidized with cyclic shear. It is likely that the saturated fill liquefied during the earthquake. Moreover, it is possible that the unsaturated fill fluidized, losing the initial shear strength during cyclic shear induced by the earthquake. The Nishisaruta landslide with similar magnitude and configuration to the Dateshita landslide occurred a few minutes after the principle motion of the main shock. Rainfall was an important feature that exacerbated the Nishisaruta landslide, whereas no rainfall had been observed for a week before the Dateshita landslide. The subsurface soil of slope of the Nishisaruta landslide was a fill with fine-graded sand, which originated from sandstone on the hill. The upper portion of the slope that lost shear strength because of liquefaction descended along the slope, and spread with high water content on the lower rice field. Numerical simulations have suggested that the saturated fill liquefied during the main shock. Residual excess pore pressure induced by the foreshock affected the slope's stability.
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  • S. J. BOONE
    2005 Volume 45 Issue 4 Pages 165-166
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
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  • CHARLES E. AUGARDE, HARVEY J. BURD, GUY T. HOULSBY
    2005 Volume 45 Issue 4 Pages 166-167
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
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  • J. N. FRANZIUS, D. M. POTTS, T. I. ADDENBROOKE, J. B. BURLAND
    2005 Volume 45 Issue 4 Pages 168-169
    Published: 2005
    Released on J-STAGE: August 13, 2012
    JOURNAL FREE ACCESS
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