A model introduced in the present paper is capable of accounting for the cyclic behaviour of sand reasonably well. The salient features of the proposed model are summarized as follows : (i) Generalized forms of Cambridge models are given to yield function and plastic potential.(ii) A combination of isotropic and kinematic hardening is achieved.(iii) A non-associative flow rule is used.(iv) The isotropic hardening involves plastic work related to not only volumetric but also deviatoric deformation.(v) A translation rule of yield surface is specified by extending Ziegler's rule of kinematic hardening.(vi) The constitutive model is capable of describing contraction as well as expansion of yield surface with simultaneous translation.Several drained cyclic tests are simulated and good comparison with experimental results is reported.

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The cap model proposed by DiMaggio and Sandler and subsequently modified by Desai et al. involves only two stress invariants. An extension of this model is proposed herein by incorporating the third stress invariant into the formulation. The model requires only one additional constant which can be obtained from simple laboratory tests. An artificial soil is tested in a truly triaxial device and the stress-strain data obtained from this test program is used to verify the model. Failure surface as well as stress-strain predictions are compared with that of experimental observations. The agreement between predictions and observations are found to be excellent.

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The behavior of clay subjected to repeated loading is an important foundation design consideration not only for structures which must resist seismic forces but also for other kinds of construction which must be capable of withstanding cyclic or intermittent loadings -such as pavements, storage facilities and off-shore structures. Clay samples under repeated loading are more compressible than those under static loading. The difference in compressibility or settlement between these two loading patterns seems to be due to secondary compression. The settlement of samples under repeated loading is caused and governed primarily by the magnitude of total load, the number of load cycles, the loading period, the load increment ratio, loading pattern and artificial cementation of the sample.This paper investigates the mechanism of consolidation of clay under repeated loading by means of considering these influencing factors. In particular, emphasis is placed upon the importance of secondary compression in consolidation under repeated loading rather than in consolidation under sustained (static) loading, because the predominant settlement in repeated loading must be ascribed to secondary compression. The proposed method of analysis is a combination of two methods ; a method which takes the effect of secondary compression into consideration is combined with a modified version of Terzaghi's theory for repeated consolidation of clay. The calculated settlement under repeated consolidation is compared to the observed settlement in repeated consolidation tests on clay samples.

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The results of finite element analyses of soils in simple shear devices, assuming that these soils can be modelled either as an elastic or an elastoplastic material, are presented. The results indicate that an elastic analysis produces larger levels of stress concentrations than an analysis using the modified Cam-clay model. The predicted stress-strain behavior of a very loose sand and speswhite kaolin using the modified Cam-clay model agrees very well with simple shear test results deduced from measurements made at the sample core of the top boundary of the samples for constant load tests. A satisfactory match of experimental and modified Cam-clay stress-strain results was not obtained for the constant height test. The simple shear devices (Norwegian Geotechnical Institute and Cambridge types) can be expected to give good quality results for monotonic loading from carefully prepared samples if measurements of stress and pore water pressures are made at the sample core on either the top or bottom or both horizontal boundaries of the sample.

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A series of in-situ experiments was performed to evaluate the well resistance of gravel drains, and to quantitatively define the preventative effects of such gravel drains on increasing pore water pressure due to earthquake motion in liquefiable sandy deposits.This paper confirms that the well resistance of the drains is extremely large although the permeability coefficient of the drain material is more than 400 times that of the deposit. Disregarding well resistance is also clarified to be impractical in the spacing pitch design of drain piles. The values of the measured pore pressure ratio during vibration are found to be easily predicted by calculation using a simple equation.

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This paper presents the effects of various cement-rice husk ash proportions on the geotechnical properties of lateritic soils. Physical properties of both rice husk ash (RHA) and original lateritic soils were determined. The influences of different mix proportions of cement and RHA on Atterberg limits, compaction characteristics, unconfined compressive strength, California bearing ratio and swelling of lateritic soils were studied. Test results show that these lateritic soils stabilized with cement-RHA mixtures can be used in highway construction. From the point of view of compressive strength, California bearing ratio and economy ; this study recommends a mix proportion of 6% RHA+3% cement for sub-base materials and 6% RHA+6% cement for base materials.

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