The effect of particle-crushing on the shear characteristics of a decomposed granite soil was investigated by a triaxial compression test and a repeated triaxial test. The increase in surface area, ΔS is used as the measure for the amount of particle-crushing, and it is shown that the amount of particle-crushing ΔS induced by the shear stresses has a close relation to the plastic work done W.The particle-crushing property of the sample under shear stresses is defined by the rate of increase of the surface area S to the plastic work done W (dS/dW), which is called the "particle-crushing rate" in this paper, and a close relation is found between the particle-crushing rate and the dilatancy rate or the shear strength.The particle-crushing property of the decomposed granite soil examined in this study is compared with that of a sand under high pressures (Miura et al., 1977), and it is concluded that the particle-crushing phenomenon of the decomposed granite soil under low pressures is substantially the same as the particle-crushing phenomenon of the Toyoura sand under high pressures.The particle-crushing phenomenon under repeated deviator stresses is also investigated, and it is suggested that the amount of particle-crushing ΔS is also a function of the plastic work done W.

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Stress components in an anisotropic soil is analyzed on the assumption that it behaves like an anisotropic-rigid-plastic material. Numerical solutions by the stress characteristics indicate that the bearing capacity factor N_γ by self-weight is easily over-estimated about 40%∼50% when the effect of the strength anisotropy of sandy soils is neglected. The bearing capacity tests by means of a small testing box also support the possibility of the over-estimation. The ultimate bearing capacity is maximum when a strip footing is penetrated perpendicular to the bedding plane, while when a strip footing is penetrated parallel to the bedding plane, the bearing capacity becomes minimum. The ratio of the maximum to the minimum is 1.6 for dense Toyoura sand. In spite of the remarkable effect of the strength anisotropy on the bearing capacity, the residual bearing capacity is constant without any effect of the strength anisotropy. On the basis of the qualitative accordance between the experimental results and the anisotropic-rigid-plastic solutions taking account of the effect of the mean pressure, it can be said that the so-called scale effect of N_γ is mainly caused by the decrease of mobilized angle φ with the increase of the mean pressure.

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A mechanical model on the stress-strain behaviour of normally consolidated cohesive soil is presented in this paper based upon the experimental results. Theoretical equations are derived based on the theory of elastoplasticity. Time effect is not taken into consideration. In the analysis, strain increment is divided into two components, i.e., elastic and plastic ones. The plastic component in strain increment is further divided into two components termed here as η-component and p-component. These components of plastic strain increment occur due to effective stress increments in the directions of constant mean effective principal stress and constant stress ratio, respectively. Corresponding to two components of plastic strain increment, two sets of plastic potential, yield function and hardening function are proposed, and nonassociated flow rule is formulated. The strain increments due to the effective stress increments in various directions are calculated by this theory.The model thus obtained for the stress-strain behaviour of soil reasonably explains the dependency of the direction of plastic strain increment on that of effective stress increment. This model is applied to the analyses of triaxial drained shear tests along various stress paths and satisfactory result is obtained. The stress-strain behaviour by this model is compared with those obtained by theories by Roscoe et al. (1963, 1968) and Calladine (1971).Discussion on the stress-strain behaviour of soil predicted by these theories including the author's one is given.

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A new style of consolidation test is proposed for the purpose of predicting consolidation constants of sediments to be formed in a dyked pond by hydraulically dredged clay materials. This new test is performed by applying the seepage force on a specimen prepared by sedimentation in a consolidometer. The principle that the seepage force is converted into consolidation stress is at first presented. It is next shown that all of the consolidation constants and the compression curve as well can be determined by performing following three measurements in the state of steady seepage flow realized after the completion of consolidation; (1) distributions of pore water pressures and of (2) water contents within the specimen, and (3) velocity of the flow passing through the specimen. With use of the test apparatus developed for this study, consolidation constants were determined in the wide range of stress from the very low stress of 0.01 kN/m² to 50 kN/m².

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Undisturbed sand samples were taken from two adjacent sites in Niigata, Japan, using an Osterberg piston sampler. One site showed serious signs of liquefaction during the 1964 Niigata earthquake and the other site showed no surface signs of liquefaction. Laboratory cyclic triaxial shear tests were performed on these specimens to determine cyclic strengths of the soils in their undisturbed insitu condition. It was found as a result of these tests that the cyclic strengths of insitu soils in Niigata were not high. Cyclic stress ratios required to cause 5% double amplitude axial strain for 20 stress cycles were on the order of 0.2 for specimens at an average relative density of 65% and on the order of 0.15 for specimens at an average relative density of 35%. There was no distinct difference in cyclic strength values between the two sites where there was and was not surface evidence of liquefaction during the 1964 earthquake.

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The aim of this paper is to study the suitability of foam propellant for the compaction of loose sand. This method is very promising in achieving compaction of loose tracks in short time and thus facilitates off road trafficability. The data presented of compaction tests by application of propellant are useful in deciding the optimum propellant quantity. It is observed that the propellant at 0.06g/cm² assures optimum compaction results.

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In the present note, a procedure to determine the correct water content of a very soft clay which contains salt in its liquid phase is proposed taking account of the salinity; such a modified procedure is required in landfilling works by use of dredged sea sediments. It is at first shown that the water content is correctly determined by employing a new quantity expressing the salinity in addition to the currently obtained water content. It is further shown that the error introduced owing to the salinity increases as salinity and/or water content increases, and the relative error reaches to 25%, for example, when the water content is 500%. A procedure of preparing soil-water mixtures with predetermined water content in finally presented.

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