The Split Hopkinson Pressure Bar method (S. H. P. B) provides a ready means for direct analysis of material dynamic response. Soil Specimens generally present poor mechanical properties, thus the classical experimental device has to be adapted. An original experimental arrangement "Three-Dimensional Split Hopkinson Pressure Bar" (3D-SHPB) is proposed. It allows measurement of the complete three-dimensional dynamic response of soils. Experiments are oedometric type tests (rigid confining cylinder) involving dynamic radial stress measurement. Pseudo Poisson's ratio is then determined and the influence of strain rate is shown. In addition, other types of confining systems are used : soft and semi-rigid confinement and low impedance tests are performed. Results on different loading paths are compared with others on sands and clays. Analysis at grain-size level gives further elements on the comminution process.

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The lateral soil pressures, bending moments, pile displacements at the ground surface, and the bearing capacity of instrumented vertical single flexible model piles in layered soil system consisting of soft clay overlying loose sand, under vertical eccentric and central inclined loads have been investigated. The results of these load tests are compared with theoretical estimates based on the concept of the effective embedment depth of equivalent rigid piles for ultimate and elastic cases. Reasonable agreement has been found between the observed and the predicted behaviour of flexible piles. The analyses are also compared with the results of some field case records.

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In order to find out the real cause leading to the anisotropy of undrained shear strength of clayey soils, two types of undrained shear tests were carried out ; 1) undrained plane strain tests on lightly over-consolidated kaolin clay, and 2) undrained triaxial tests on heavily over-consolidated kaolin clay. Analysis of the data has shown that the anisotropy of undrained shear strength of over-consolidated kaolin clay is primarily caused by the direction-dependent (anisotropic) shear strength parameters c' and φ' in terms of effective stresses. The anisotropy of pore water pressure parameter A_f is artificially generated as a result of the anisotropic change of the undrained shear strength itself, rather than of the anisotropic excess pore-pressure development during shearing, and is of secondary, if any, importance to interpret why the undrained shear strength is anisotropic. Intensity of the anisotropy in the undrained shear strength is not altered much by either changing the boundary conditions, such as triaxial and plane strain or increasing the over-consolidation ratio up to 32. The minimum values of cohesion c' and friction angle φ' appear when a specimen is compressed with the major principal stress inclined at about 30° to the consolidation plane. When a specimen is compressed either normal or parallel to the consolidation plane, values of cohesion c'and friction angle φ' are high with no significant difference between them. The difference between the maximum and the minimum friction angle φ'is almost the same as that observed in the triaxial tests of sands. In the case of sands, however, a specimen compressed normal to the bedding plane yields the maximum friction angle φ', while a specimen compressed parallel to the bedding plane yields the minimum value in the triaxial tests and a value close to the minimum in the plane strain tests. These observations suggest that the micro-deformation mechanism leading to the strength anisotropy is quite similar in both clay and sand, but not exactly the same.

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In this paper, the behavior of soil stabilized by ferrum lime, a mixture composed of ferric oxide (Fe₂O₃) and hydrated lime (Ca (OH)₂), is investigated in order to assess the engineering properties of the stabilized soil for its application to road construction. The aptitude of the ferrum-lime stabilized soil as road base material is evaluated according to the static compressive, static flexural, and dynamic resilient properties of materials obtained from laboratory tests. The ferric oxide promotes an increase in both compressive strength and the stiffness of the stabilized soil. Resilient modulus M_r, a parameter expressing the material behavior under dynamic cyclic loading, depends on the deviator stress and the mean principal stress. Under lower deviator stress and mean principal stress conditions, the M_r of the ferrum-lime stabilized soil has a higher value than that of the hydrated-lime stabilized soil. However, the difference in resilient modulus M_r between the two types of stabilized soils may not be distinct with increases in the deviator stress and the mean principal stress. In addition, the dependence of resilient modulus M_r on the static strength of the ferrum-lime stabilized soil can be observed. Fracture surface energy γ_s, a parameter which indicates the resistance ability of a material to cracks, is related to the deflection at failure, but hardly depends on the flexural strength. The γ_s has almost the same values for both type of stabilized soils. According to test results, ferric oxide can improve the durability of pavement when it is used as a stabilizer for lime stabilized soil.

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Reinforced soils exhibit an improvement in strength and deformation characteristics under monotonic loading conditions, due to the additional "pseudo" confinement caused by the lateral restraint and shear stress mobilization along the soil-inclusion interface. In this paper, the influence of the lateral restraint on the cyclic behavior of the soil is investigated. Experimental results obtained from cyclic triaxial tests on a partially saturated reinforced silt are presented. The reinforcement consists of horizontal discs of woven and non-woven geotextile equally spaced along the specimen. The influence of loading level, geotextile type, reinforcement spacing, and specimen diameter are examined. An analytical procedure to interpret the results, based on the confinement enhancement model, is proposed. In the procedure, the effect of the additional equivalent confinement on both the strength and stiffness of the soil is considered.

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The mechanical properties of sands change notably with a variation of confining stress. In some geotechnical problems, such as the bearing capacity problem of shallow foundations on sand ground, the confining stress dependency of sand mechanical behavior plays an important role as a stress level effect. In this study deformation-failure behaviors of some 80 granular materials with various primary properties were observed in a series of triaxial compression tests covering a range from low to medium high confining stresses. From experimental results, the dependency of the deformation-failure behaviors of sands on confining stress was comparatively examined, and the degree of confining stress dependency was evaluated by the indices introduced in this study. The influence of primary properties, such as density, hardness, shape and size of grains, on the degree of confining stress dependency is the main subject of this study. From test results, it was found that the mechanical properties of sands vary markedly with a change in confining stress, and the degree of confining stress dependency varies with the primary properties. The degree of confining stress dependency can be estimated from some index properties ; void ratio extent (e_max-e_min) was selected as a promising parameter for evaluating the confining stress dependency of the deformation-failure behaviors of sands.

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It is well known that even a single soil shows different mechanical properties with variation in any of many influencing factors. Among these, the density of soil is a most important factor in many geotechnical problems such as subsidence of ground, stability of soil structures and liquefaction potential of sandy soils. Density is a key to reliable answers. In this study some 80 granular materials were used, and triaxial specimens with several relative densities were prepared ; a series of conventional drained triaxial compression tests were conducted on the specimens. From experimental results, the dependency of deformation-failure behaviors of sands on relative density was comparatively examined, and the degree of relative density dependency was evaluated by the indices introduced in this study. The influence of promary properties, such as density, hardness, and shape and size of grains, on the degree of relative density dependency is discussed, as a subject of this study. It was found that the degree of relative density dependency is variable with primary properties. The degree of relative density dependency can be estimated from some index properties ; void ratio extent (e_max-e_min) was selected as a promising parameter for evaluating the relative density dependency of deformation-failure behaviors of sands.

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The Cam-clay models were originally developed through theoretical considerations and experimental results under triaxial compression condition, and extended to three-dimensional models by using stress parameters p and q. A criterion of the Extended Mises type was adopted for the shear yield and failure of clay in Cam-clay models. However, it is well known that the failure of soil is not explained by the Extended Mises criterion but by a criterion of the Mohr-Coulomb type or the SMP (Spatially Mobilized Plane) type and others. Taking the consistency in the shear deformation and the shear failure into account, it is quite natural to introduce the Mohr-Coulomb or SMP criterion for the shear yield as well as the shear failure of soil. In this paper, a transformed stress tensor σ_ij is proposed, which is deduced from what makes the SMP criterion become a cone in the transformed principal stress space. The transformed stress tensor σ_ij is applied, as an example, to the Cam-clay models to improve their capability to describe the behavior of soils in general stresses including triaxial compression. The Cam-clay models revised by the transformed stress tensor σ_ij can explain well the drained and undrained behavior of clay not only under triaxial compression, but also under triaxial extension, plane strain, and true triaxial conditions. The present paper provides a reasonable and simple approach for extending the models using stress parameters p and q to the three-dimensional models by adopting σ_ij instead of σ_ij.

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This paper is a study based on a number of model tests of free- or fixed-headed pile groups, each composed of nine piles, subjected to lateral loading. The model piles made of aluminum were set in dry sand and laterally loaded. The behaviors of the pile groups were then analyzed by the 3-D elasto-plastic finite element method (FEM), which represents a realistic model to simulate the problem. This model includes elasto-plastic soil behavior with no-tension characteristics, as well as thin frictional elements for slippage on the pile-soil interface. Parameter values for the sand used in the analyses were determined from conventional triaxial compression tests. It is shown that the experimental results can be precisely simulated by the analysis. Furthermore, field tests of a prototype foundation of steel pile group (3×3 piles) subjected to lateral loading at its footing were performed. The 3-D FE analyses were conducted to simulate the results. Parameter values for FEM have been adjusted, using the back analysis technique, so as to simulate a load-displacement curve obtained from the single pile loading test. As for the lateral load-displacement relationship and the bending strain distributions along each pile, a good correlation between the experiments and the analyses can be seen in the case of the pile group.

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This study provides detailed discussion on the shear characteristics of natural sand samples collected from various locations in Japan, based on the results of triaxial compression tests. The main conclusions are : (1) The sand classification chart proposed by Fukumoto properly reflects the shear characteristics of sands, and is appropriate for practical use ; (2) Mogami's formula fits very well to the relationship between the angle of shear resistance φ_d and the void ratio e_i ; (3) As suggested by Moroto, a linear relation is clearly found between the coefficient k in Mogami's formula and the minimum void ratio e_min.

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