A series of undrained triaxial compression tests was performed on Toyoura sand in order to investigate the behavior of sand under large deformation. The present study focuses on the effects of anisotropic consolidation on the undrained behavior of sand. A wide range of initial states of sand is covered and taken into account with the behavior of sand varying from contractive to dilative. Different states of consolidation stress were shown to affect the stress-strain behavior of sand and the development of excess pore water pressure up to an axial strain of 5%. Beyond a strain in excess of 10%, the behavior of sand was shown to become independent of the stress state at consolidation. Consequently, the relation between void ratio and confining stress at steady state and quasi-steady state are independent of the extent of anisotropic consolidation. Moreover, the initial dividing curve between dilative and contractive behaviors in an e∼p'diagram was shown to move down as the sand is more anisotropically consolidated.

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Several studies have concluded that the effect of matric suction on the shear strength of unsaturated soil is very important. However, little attention is given to the stress history due to unsaturation and drainage condition in the arrangement of these experimental results. This paper attempts to show the relationship between shear properties and matric suction under a specified stress history and drainage condition. In this study, an unsaturated specimen is set up by dehydrating the normally consolidated soil with controlled matric suction to a specified stress history. Triaxial apparatus and hollow cylindrical torsional shear apparatus are employed to examine the effects of stress history and drainage condition, respectively. Through systematic experiments, the effects of stress history and drainage condition on the stress-strain relationship are clarified. The increase in shear strength by matric suction which is measured at the point of maximum shear stress is observed to be independent of stress history and drainage condition. However, in strain softening behavior it was found that the ultimate strength is independent of matric suction and traces a unique line which is parallel to the critical state line on the p_net-q plane.

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This paper investigates the behavior of real progressive failure of reinforced foundations. Firstly, a series of model loading tests on unreinforced and reinforced foundations are carried out, in which the ground is modeled by aluminum rods. Based on the results of these tests, not only the bearing capacity but also the mechanism of progressive failure are investigated using image processing, analyzing the photographs on the progress of failure at every settlement level. The movement and the micro-rotation of aluminum rods are obtained by experiment. From the analytical procedure, the maximum shear strain and rigid rotation (macro-rotation) are determined. Thus, the progressive failure of reinforced foundations is discussed comprehensively from the above microscopic observation and these analytical results. The results achieved through this paper are fundamental on the localization of deformations and progressive failures of reinforced foundations. These results may provide important information for future designs.

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In this paper, a new estimation method is presented for the toe bearing behavior of non-displacement piles embedded into bearing strata of sand. The method is developed by numerical experiments. First, a new in-situ test is proposed whose results can identify five parameters of a bearing stratum uniquely. These are parameters of the stressstrain relations of sand and coefficient of earth pressure at rest. In the in-situ test, a cylinder of, for example, 10 cm in diameter is embedded into the bearing stratum. The measured results are a load-settlement relation at the end of the cylinder and a friction-settlement relation on the surface of the cylinder. These relations are back-analyzed, using elastic-plastic finite element method and neural network, and the parameters are identified. Then using the identified parameters, the toe bearing behavior of a pile is estimated by the elastic-plastic finite element method. The estimation method can be applied to piles embedded into over-consolidated sand as well as normally consolidated sand.

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In urban areas, where many of the high-rise buildings are supported by pile foundations, the number of softground tunnels has increased rapidly during recent years. To minimize the risk of damage as a result of tunnel construction the engineer who designs a tunnel needs to be able to make reliable predictions of the ground deformations induced by tunnelling and their effects on any adjacent pile foundations. In this paper, a closed form solution, developed by the authors, is used to assess the displacement field around the tunnel. The displacements estimated are then imposed on single piles and pile groups in simplified boundary element analyses to compute pile and pile group responses. The analytical method presented in this paper was verified with a case history and with numerical results obtained using FLAC^3D computer software. Comparisons are made to evaluate the group action for various pile group configurations. The influence of various pile lengths and pile locations from the tunnel is also presented.

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It is commonly accepted that the yield point during one-dimensional compression is related to the initiation of marked particle crushing. Different materials have clear to very amorphous yield points depending on the compression line curvature. In order to examine the relationship between the curvature and slope of the compression line and the statistics of individual particle crushing taking into account particle size and overall grading, high pressure onedimensional compression tests on silica sand samples seeded with marked particles were carried out. Five levels of particle damage were obtained and defined from microscopic observations of the particles before and after testing. A statistical analysis was carried out on the data for the observed levels of damage to investigate the frequency variation with increasing applied stress. Additionally, one-dimensional compression tests were conducted to examine the effects of initial void ratio and grain size distribution on soil crushability and consequently the compression behaviour. It was found that even for the same material the yielding characteristics were dependent on the grading curve with much more marked yielding occurring for uniformly graded sands in comparison with well graded sands. This was related to the nature of the microscopic particle crushing during yielding. As the material changed from uniform to well graded, the nature of the particle crushing changed from the sudden catastrophic onset of splitting to the gradual splitting of smaller size particles, breaking of the smaller asperities and grinding of the surface.

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Two soils with low plasticity are investigated ; intermediate soil from Ishinomaki, Japan and lean clay from Drammen, Norway. Since both the soils were retrieved using the Japanese sampling method, the test results from these samples are comparable. Though they have the same order of plasticity index (I_p), there is a significant difference in the grain size distribution characteristics between these soils. Ishinomaki intermediate soil contains a lot of sand or silt sized particles, its I_p value being nearly proportional to its clay content. On the other hand, Drammen clay consists of a large proportion of rock flour, which contains little clay mineral. The study shows that the unconfined compression test significantly underestimates the undrained shear strength for both soils, and their residual effective stress (p'_r) is also very low. It has been found that to compensate for loss of p'_r, recompression tests are useful methods to evaluate the strength of such soils.

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Particle crushing is a progressive phenomenon. This study examines time-dependent behavior due to particle crushing. A review of the literature was made to find evidence of time-dependent behavior due to particle crushing. Single particle crushing tests and one-dimensional compression tests were carried out on four crushable materials with careful visual observations. The mechanism of time-dependent compression was discussed. The following observations were made : (1) The time-dependent behavior under one-dimensional compression stems mainly from a repetitive cycle of crushing, rearrangement of particles and redistribution of contact stresses. (2) Crushing patterns and rearrangement in one-dimensional compression tests are different depending on the characteristics observed in single particle crushing tests.

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