A series of K₀-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world in order to investigate the behavior during K₀-consolidation tests and evaluate K₀-values that are required for laboratory tests with recompression techniques, FEM analysis using elasto-plastic constitutive equations, etc. It was confirmed that the famous equation K_0NC = 1-sinφ' is useful; however, the definition of φ' should be concerned. Inthe case using φ' corresponding to a critical state line, i.e. (q/p)_max, the equation underestimates K_0NC by 0.05 ; in contrast, in the case using φ' corresponding to a peak strength, i.e. (q)_max, the equation overestimates K_0NC by 0.05. This study proposes a procedure for estimating the in-situ K₀-value. For a representative undisturbed clay sample, K₀-consolidation and K₀-overconsolidation tests (i.e. SHANSEP test) are consecutively carried out to obtain the K-OCR relationship. Using the profile of OCR obtained from a series of oedometer tests, the K-value corresponding to the OCR can be calculated as the in-situ K₀. The K₀-values obtained from both the K₀-overconsolidation test corresponding to the OCR in the laboratory and the flat dilatometer test (DMT test) in the field compared well.

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The paper examines the axi-symmetric problem related to a loaded thin flexible disc inclusion embedded in bonded contact with a cross-anisotropic layer. The solution representations governing the cross-anisotropic layer are given in a convenient matrix form. The associated mixed boundary value problem is reduced to two coupled Fredholm integral equations of the second kind, in which the deflection of the disc is expressed by the stresses applied on the disc in an analytical way. The equations are evaluated numerically. Numerical results presented in this paper illustrate the influence of the anisotropy, the relative thickness of the layer and the relative rigidity of the disc on the load-deflection behavior of the disc for a wide variety of material and geometric conditions.

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This study examines the phenomenon of settlement induced by traffic loading on low embankment roads built on soft cohesive soils deposited in a reclaimed lowland. A series of cyclic triaxial tests were conducted on undisturbed soft Ariake silty-clay under undrained and partially-drained conditions. A model based on the test results is proposed to simulate the partially drained behavior of silty-clay under a variety of lateral stresses. It is shown that the maximum excess pore pressure generation ratios and volumetric changes increase until the cyclic stress ratio reaches a value of 0.73, which is independent of the effects of lateral stresses under the same anisotropic consolidation ratio. Numerical analyses applying the proposed model were performed to compare the effects of soil thickness and cyclic loading time during one day and one cycle on partially drained cyclic behavior. It was found that a large ratio of cyclic to non-cyclic loading time during one cycle exerts a smaller influence on volumetric strain than the total time of cyclic loading during oneday. Observed settlement results of a low embankment road are analyzed to verify the applicability of the proposed model.

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This paper proposes a method to estimate in-soil deformation behavior of geogrid based on the results of direct box shear tests. A series of drained direct box shear (DBS) tests were performed, consisting of two types of normal stress loading methods and a series of pull-out tests in which the space of the pull-out opening, embedded length of geogrid and conditions of in-soil end restraint were changed. Comparisons were made between the calculated in-soil deformation behavior of the geogrid based on the results of the DBS tests and that of the results observed by pull-out tests. Based on this study, the following findings were obtained. Strength parameters corresponding to the peak or the residual states obtained from the two types of direct box shear tests almost coincide with each other. Using the method proposed in this paper with the strength parameters obtained by DBS tests, it is possible to estimate the in-soil behavior of geogrid. As the pull-out force vs. pull-out displacement relationships depend not on the conditions of in-soil end restraint of geogrid but on the normal stress exerted on the geogrid, it is important to construct a reinforced soil structure so that sufficient frictional resistance develops between soil and geogrid.

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This paper investigated the transverse horizontal load on buried pipes due to liquefaction-induced permanent ground displacement in the horizontal direction. The focus of study was on the maximum load. For this purpose, liquefaction-induced permanent ground displacement in areas behind quay walls and in inland sloping ground areas was reproduced in a model ground and the load exerted on pipes buried in this ground area was measured. The investigation employed dynamic centrifuge model tests. All pipes were buried in non-liquefaction layers situated above liquefaction layers. All of the obtained load due to liquefaction-induced permanent ground displacement in the horizontal direction were much smaller than the load obtained by moving pipes forcibly in a static ground. The ratio of the maximum load due to liquefaction-induced permanent ground displacement to that obtained by moving pipes forcibly was about 0.3-0.4. There is a possibility that a maximum load corresponding to the residual strength of the ground was exerted on the pipes. The ground displacement patterns suggest that large shear strain was generated on the rear side area of the pipe. The cracks on the front side area of the pipe may have decreased the confining pressure of the ground and resulted in the decrease of the load. The tensile strain generated in the ground may have decreased the confining pressure and resulted in a decrease in the load as well.

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A new construction procedure applying a large preload to a mechanically reinforced backfill structure and keeping a large prestress while the structure is in service is described. This construction procedure was developed to substantially decrease transient and residual compression of reinforced backfill by long-term vertical cyclic loading, such as traffic load. A very high performance for about four and a half years of a prototype railway bridge pier of preloaded and prestressed geogrid-reinforced gravel backfill, which validated the advantages of this construction procedure, is described. A series of model loading tests performed in the laboratory to find the relevant preloading and prestressing procedure are described. It is shown that the transient and residual compression of reinforced backfill by vertical cyclic loading can be made very small by preloading the reinforced backfill and then decreasing the load level to a prestress level that is about a half of the preload level, while keeping the difference between the preload and prestress levels sufficiently larger than the amplitude of subsequently applied cyclic load. Effects of different combinations of backfill soil type and reinforcement material, the use of tie rods and the application of pre-cyclic preloading are reported. Negative effects of the swelling of backfill during unloading are discussed.

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Induced anisotropy under three-dimensional stress conditions is one of the important factors in the accurate prediction of ground deformation and should be a primary consideration not only in the laboratory, but also in the field. To achieve this objective, torsional shear tests for saturated cohesive soils with induced anisotropy were performed. Induced anisotropy was generated by the shear history under constant p' (effective mean principal stress), a (direction of major principal stress) and b (intermediate principal stress coefficient) conditions in this study. The parameters a and b were also set up during the shear history process, and the drained torsional shear tests were carried out under constant p', a and b conditions using these specimens. The behaviour of soils during this process was examined in detail. The elastic boundary induced by the shear history was represented in three dimensional space. Furthermore, the uniqueness of this elastic boundary was examined by changing the stress level and the material of the specimen. In conclusion, the uniqueness of the elastic boundary induced by the pure shear history (constant p') on saturated cohesive soils was verified via these experimental results. The application of the elastic boundary in a wide range of stress level and material was thus shown.

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The vertical uplift resistance of shallow strip and circular plate anchors buried horizontally in a two layered sand has been determined by using the upper bound theorem of limit analysis. Uplift factors f_γ and f_q due to the effects of soil unit weight and surcharge pressure, respectively, have been established. For a given thickness of the two layers, the uplift factor f_γ is found to be comparatively greater when the anchor is embedded in dense sand underlying a loose sandy layer. However, the factor f_q remains unaffected by the layers' relative positions. As compared to available experimental results, the theory provides a slight overestimation of the uplift resistance especially for greater embedment ratios.

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