Marston (1930) theory of earth pressure on buried structures is reevaluated using a transform function first proposed by the Author, Poorooshasb (1982) and taking into consideration the relative rigidity of the buried structure. It is shown that the development of the frictional resistance along vertical planes projecting from the two sides of the box is dependent, not only, on the depth of the overburden but also a function of the relative rigidity of the structure itself. The paper is concluded by comparing the result from the present analysis with those obtained from the Marston theory.

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An apparatus was designed for one-dimensional seepage-failure tests. The apparatus consists of seepage cylinder, constant-head device, and open piezometers. Using the apparatus, a series of seepage-failure experiments on the one- and two- Iayered sand columns was carried out. It was found that the flow condition : (i) k_[○!F]/k>15 (exerted-pressure type) or (ii) 1<k_[○!F]/k<5 (uniform-flow type) is one of the most important factors in the seepage failure of sand columns, where k_[○!F] and k are the coefficients of permeability of the rectifying filter and the sand layer, respectively. The following results were then obtained : (1) The modes of failure of sand columns are able to be predicted theoretically from the residual effective stress diagrams. (2) The one-layered sand column (with no loaded filter) collapses in quite different ways according to the above two flow conditions. (3) In the case of the flow condition of the exerted-pressure type, a multi-layered sand column collapses at the smaller hydraulic head difference than that in the uniform-flow type. (4) When the relative density D_r is small almost all the one-layered sand columns (with no loaded filter) collapse at the smaller hydraulic gradient than the theoretical critical one. (5) As the residual effective stress within a sand column increases, the friction between the vertical cylindrical surface and sand particles becomes large, and thus the resistance to failure of the sand column increases. As a result the sand column collapses at the larger hydraulic head difference than the theoretical critical one. (6) The effect of the cylindrical surface friction on the critical hydraulic head difference of a sand column is able to be estimated from a magnitude of the residual effective stress.

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The Limit Equilibrium Method (LEM) is an empirical technique, and the characteristic of its solution has not been clarified yet. The authors have been studying LEM in which slices or blocks are used to represent the sliding mass, and they suggested that LEM is a method which satisfies the necessary condition of Slip Line Method (SLM), because a block cut out from the stress field obtained by SLM always satisfies the limit equilibrium condition for LEM. Then, the authors have proposed Generalized LEM (GLEM), in which triangle or quadrangle blocks can be treated and safety factors are defined both on the base planes of blocks and on interblock planes. In this paper, the validity of the assumption on interblock forces is investigated, and a new formulation of GLEM using the displacement rate field and the principle of virtual work is introduced. Then, it is shown that the solution by LEM may sometime equal to one of LBM (Lower Bound Method) and sometime one of UBM (Upper Bound Method), depending on the assumption of interblock forces or interblock safety factors. To show the evidences, two GLEM solutions of a bearing capacity problem are demonstrated each of which completely agrees with either lower or upper bound solution. To obtain an upper bound solution closer to the actual one, the adjustments of block geometry during the minimization of bearing capacity are required in GLEM.

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In this paper earth retaining walls reinforced with geotextiles are investigated. The failure model considered is a special internal one, where the failure plain cuts through the geotextile layers. Horizontal earthquake forces are introduced to allow a seismic resistant design. Parametric studies indicate that, for the failure model considered, the toe of the reinforced wall is its most sensitive part. Based on the probabilistic safety concept a reliability analysis is carried out and design factors are derived, which permit the assessment of the safety of the structure in an easy and convenient way. More detailed earthquake related studies are carried out in order to compare the design situation between Tokyo, Osaka and Kyoto. It is found that the construction of reinforced earth retaining structures appears to be feasible in Osaka and Kyoto, whereas in Tokyo, because of its prominent earthquake record, especially the toe of the wall has to be designed with great caution in order to ensure the probability of failure to remain acceptably small.

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On large-scale reclamation works, the consolidation settlement of diluvial clays which lie deep underground should be discussed. The diluvial clay in Osaka Bay is in a quasi-overconsolidated state by cementation bonding. The values of the compression index and the void ratio are very large in spite of the large overburden pressure. Therefore, its consolidation characteristic is considered to be different from that of the alluvial clay. In this paper, a series of long-term consolidation tests is carried out, and it is revealed that the value of coefficient of secondary compression (Cα) under a load in the quasi-overconsolidated region becomes to be that in the normally consolidated region as time elapses. Considering the effect of strain rate, this result shows that the yield stress is dependent on the strain rate. This also means that even if a clay behaves as an overconsolidated clay in the test, it might behave as a normally consolidated clay in the site. Therefore, it should be considered that the in-situ secondary compression settlement was underestimated if it was calculated by using C_α of the laboratory test. In addition, the settlements on two reclamation works in Osaka Bay are calculated by a proposed long-term settlement analyzing method using strain rate and time relationship, and the results are in good agreement with the observed settlement data at sites.

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An anisotropic elasto-plastic constitutive model is presented in triaxial space in order to evaluate the stress-strain behaviour of anisotropically consolidated sands over a wide stress range for static loading conditions. The fundamental concept presented herein is based on the assumption that sand exhibits anisotropic hardening, dependent on both plastic volumetric and shear strains. The model presented consists of a yield function, plastic potential and hardening modulus, which are formulated based on a few basic assumptions and experimental evidence. The model contains eleven experimental parameters which are determined from a few conventional triaxial tests and also have a clear physical meaning. The predicted behaviour for drained and undrained triaxial tests is compared with available experimental data. It is shown that the model accurately represents the changes with increasing confining pressure in stress-strain behaviour for anisotropically consolidated sand.

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It has been recognized that the Dupuit theory of unconfined flow is applicable to the determination of a free surface of flow in an earth dam which has a section with vertical slopes, and built on an impervious foundation. If the earth dam has a partially penetrating cutoff wall, there is no easy method to determine the free surfaces in the dam. For the above cases, the trial-and-error method has been carried out conventionally to determin the free surface in the earth dam with a penetrating cutoff wall. This paper describes a new numerical analytical method which enables us to easily obtain the free surfaces in the earth dam with a partially penetrating cutoff wall. In this method a curved boundary is transformed to a linear boundary by the Zhukovsky's function, and the solution of the Laplase's equation is obtained in the mapping area which satisfies the linear condition with regard to velocity potential. Then the actual free surface and length of cutoff wall in the definition diagram can be obtained by means of inverse mapping using the results of the above mentioned calculation. The authors made the experiments using sand-models with the same boundry condition as the case of analysis in order to validate the accuracy of the results of the analysis method.

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The constitutive relations based on the endochronic theory have been presented to describe the behavior of overconsolidated clay subjected to cyclic loading. The proposed constitutive law is capable of describing (a) strain softening and hardening, including a softening steady state which is eventually reached as the number of cycles increases; (b) densification and dilatancy; (c) effect of effective confining pressure; (d) effect of overconsolidation ratio OCR. The model is applied to describe the strain-controlled cyclic undrained triaxial test data on Shanghai clay carried out by the second author and strain-controlled undrained simple shear test data on Drammen clay (Andersen et al., 1980). The comparison between the theoretical prediction and the test data shows that the presently proposed model provides a reasonable description for the clay under consideration.

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This paper makes use of Rankine's analysis to find the active and passive stresses acting on any plane in a homogeneous isotropic dry sand mass. The results are applied to the slanting wall problems. Both active and passive stresses are linearly distributed along the wall. As a result, the active and passive thrusts act at lower one-third height of wall. In general, Rankine's solution is comparable to the Coulomb's for active case; but, for passive case, Rankine's thrusts are usually lower than Coulomb's, because the direction of thrust obtained in the Rankine's analysis is not comparable to the Coulomb's direction of thrust when using a conventionally defined friction angle.

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The paper presents the results of a series of tests using the hollow cylindrical apparatus on the flow of sand during loadings involving rotation of principal stress direction. The results establish an important feature of the flow of sand during principal stress rotation, namely, nonuniqueness of flow or the dependency of the plastic strain increment direction on the stress increment direction. This feature contradicts the usual assumption in plasticity theory of a unique flow during loadings causing plastic deformations in a material. Guided by the results of the experiments, a plastic potential theory capable of representing the dependency of the flow of sand on the stress increment direction is proposed. Comparisons with the experimental results and the outcome of stress probe experiments show the validity of the proposed theory.

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By comparing the behavior of undisturbed clay samples with that of remolded samples, the effect of aging on the mechanical properties of marine clays was discussed. The compression index C_c and the secondary compression index C_α of natural aged clays show peak values when the consolidation pressure is slightly larger than the consolidation yield stress. The compression index ratio r_c, which is newly introduced in this study, is considered to be a useful index to represent the aging effect of natural clays. The values of r_c of Japanese alluvial clays range from 1.0 to 3.0 and they are smaller than those of East Canadian clays which are well-known as an aged clay. By consolidating clay slurry at a high temperature and cooling it after the completion of consolidation, remolded clay samples, whose mechanical properties are similar to those of lightly aged clay, can be produced in laboratory. The main cause of the effect of the high temperature consolidation seems to be the acceleration of cementation action. This procedure is useful to simulate the behavior of natural clay using laboratory tests of the remolded clays.

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Numerical studies of shear modulus and fabric for sphere assemblies were performed by a discrete element code, TRUBAL. Results of numerical experiments were compared with physical experiments. In general, numerical experiments simulate the stress-strain behavior and shear modulus of physical results quite well both qualitatively and quantitatively. Shear modulus has a close relationship with the coordination number. After a cycle of loading and unloading, there is an induced anisotropic fabric and are locked-in inter-particle shear forces which reflect the previous stress history. This is also reflected in a decrease in both the shear modulus and the coordination number. During reshear locked-in inter-particle shear forces would influence the behavior of shear modulus. When resheared in the previous direction inter-particle shear forces decrease first which results in an increase of shear modulus in the initial portion of loading. While resheared opposite to the previous direction initially high inter-particle shear forces would decrease the shear modulus.

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The excess pore pressures and effective stress variations in a porous seabed are measured at a breaker zone in real ocean environment. The wave-induced liquefaction is examined on the basis of the liquefaction criterion proposed by the authors. The oscillatory pore pressure, which is one of the dominant factors causing the wave-induced liquefaction, is theoretically estimated to compare with the observed data. The major conclusions drawn from the study are : (1) The effective stress in the seabed varies periodically in accordance with the propagation of ocean waves, (2) The variation of the vertical effective stress is expressed by the difference between the wave-associated bottom pressure and the oscillatory pore pressure in the seabed, (3) The oscillatory pore pressure induced by the irregular waves can be estimated by the equation proposed by the authors, (4) The liquefaction potential in the seabed can be evaluated on the basis of the proposed liquefaction criterion, (5) The wave-induced liquefaction is closely related to the upward seepage flow induced in the seabed by the rapid lowering in the sea surface during the passage of wave trough.

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The effect of preconsolidation period on cyclic strength of a reconstituted clay was investigated using cyclic triaxial tests. It was indicated from the test results that cyclic strength of underconsolidated clay was more uniquely defined by the degree of consolidation in terms of effective stress than volumetric strain. Further, by using undrained static strength instead of effective stress in normalizing cyclic shear stress, we obtained a very unique relation between the cyclic shear stress and the number of load cycles which is not influenced by the consolidation time. This is because the undrained strength is directly proportional to the magnitude of effective stress developed during consolidation. Thus, a new cyclic stress ratio using undrained static strength instead of effective confining pressure was proposed to define the cyclic strength of clay.

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The cause of shallow-depth slope failure triggered by heavy rainfall was studied by performing in-situ investigation of soil conditions at four sites of recent slope failures in Japan. The investigation included soil sampling, laboratory testing to determine the strength parameters and slope stability analyses. The results of the study showed that, in the case of near-surface sliding occurring on a slope of 30°to 45° angle, the reduction in strength due to infiltration of water into the soil was the major cause for triggering the slope failures.

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Pore pressure development in undrained loading, and ratio of undrained strength to initial effective stresses can be linked to the geometry of the undrained effective stress path. This geometry can be characterised in a fundamental way by the ratio of initial to final mean effective stresses. Although values of this ratio can in principle be estimated using an elastic-plastic soil model such as Cam clay, the variation with angle of shearing resistance or plasticity thus estimated does not correspond with field observation.

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