This paper is concerned with modeling of thermomechanical failure of triaxial specimens of saturated clays of low porosity. Thermomechanical failure manifests itself in undrained conditions as a development of advanced irreversible strains due to heating under constant total stress. In experiments on two clays the failure occured at temperatures from 70° to 90°C. The observed failure is associated with a pore water pressure buildup. Models of thermoplastic behavior of skeleton and of thermal volume changes of adsorbed water are employed to interpret and numerically simulate the test results. Using these models, thermomechanical failure was found to occur when the effective stress is brought to the critical state by expansion of pore water and thermoplastic compressive strain in skeleton.

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The undrained behaviour of a natural clayey sand from the site of the Gullfaks C oil production platform in the North Sea is described. The material shows significant undrained brittleness in triaxial compression and extension. Variables that are examined include : clay content, granular void ratio and consolidation history. The behaviour of the natural clayey sand is compared to that of a model soil formed from Ham river sand and kaolin. Differences in response are ascribed to differences in grading between the two materials.

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A method for evaluating system compliance and membrane compliance is proposed. Only changes in pore pressure and axial stress due to undrained cyclic loading at small shear strain amplitude are necessary to evaluate the value of system compliance ratio C_R. Pore pressure coefficient B-value is also necessary to calculate the value of membrane compliance ratio C_RM. These parameters can be obtained by nondestructive tests before destructive tests with large strain amplitude on soil specimens. The proposed method is applied to both reconstituted and undisturbed specimens. The test results imply that : (1) For reconstituted specimens, the values of normalized membrane penetration S calculated by C_RM indicate satisfactory consistency with other investigators' results. Therefore the values of C_RM can be successfully estimated by the proposed method. (2) A treatment for minimizing the unevenness of lateral surface of undisturbed specimens, has an effect of reducing the value of C_RM. (3) For undisturbed samples tested in this study, the values of C_R calculated by the method gave a consistent explanation of differences in pore pressure response characteristics of the specimens from the view of influence of the lateral surface treatment.

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The properties of grouted sand strength were examined by changing the pure grout strength and the density and particle size of sand over a wide range. It was found that there are limits within which the grouted sand strength is proportional to the density of the sand. There are also limits within which grouted sand strength is not proportional to the density of sand. This report examines the relationship between grouted sand and pure grout strength over a wide range of sand conditions. The relationship between grouted sand strength and pure grout strength is expressed by an exponential equation which is then examined by the Mohr-Coulomb failure criterion and the two-phase composite system. As a result, it is possible to estimate the unconfined compressive strength of the grouted sand by examining the physical properties of the sand and the strength of the pure grout being used. Regardless of the kind of sand used, the accuracy of strength obtained by estimation has a correlation coefficient of greater than 90%.

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The undrained cyclic triaxial behaviour of saturated sand was studied using isotropically and anisotropically consolidated specimens. The strength and deformation under various combinations of initial static and cyclic shear stresses were considered. The cyclic strength was first discussed, and the residual shear strain was then investigated related with effective stress ratio at the end of each stress cycle. Further, a unique relationship was found between a relative effective stress ratio η^* and the cyclic strength ratio R/R_f, where η^* is the relative position between the initial and failure effective stress ratios, and R/R_f the ratio of the amplitude of cyclic shear stress to cyclic shear strength in arbitrary number of cycles. An empirical model was finally proposed for evaluating the development of pore pressure and residual shear strain of saturated sand subjected to various initial static and subsequent cyclic shear stresses.

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Analysis of the settlement at five sites on San Francisco Bay Mud and two sites on Boston Blue Clay has shown that where dessicated crust has developed on the clay, spatial variations in the preconsolidation pressure are the most important cause of differential settlements. A simple probabilistic method is described that can be used to establish confidence limits for settlements at sites with a desiccated crust. Variations in preconsolidation pressure are accounted for by estimating confidence limits for a parameter termed the "radius of preconsolidation." Application of the methodology to the settlement of fills on San Francisco Bay Mud and Boston Blue Clay has shown that the method produces results in good agreement with field measurements and that it is suitable for use in practice. The method can be used for clay deposits which have an overconsolidated layer and requires no more testing than is performed for conventional settlement analyses. However, unlike conventional settlement analyses, it provides an estimate of the likelihood that the settlements will vary from the mean by a given amount due to spatial variations in soil properties.

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Large amount of gravel is sometimes used in compacted soils. Special compaction tests are recommended^{1, 2)} to determine the maximum dry density of the total material under such condition. Such tests are time consuming and costly, therefore, a general formula for determining densities including oversize perticles is presented in this paper. The proposed formula yields good densities even when the gravel content of the total material is high.

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The framework of a methodology proposed by the authors to evaluate the permanent deformation of embankments due to earthquake motions is briefly presented first. In the proposed method, both static and dynamic stress analyses are performed by the finite element technique to determine the stress conditions of the finite elements in an embankment both before and during an earthquake. Based on the characteristic features of the dynamic stresses during earthquakes, static and dynamic stresses are applied to laboratory specimens to simulate the in-situ stresses as precisely as possible. The moduli of the soils used in the original static analysis are modified through softening parameters in accordance with the residual strain potentials of each element. Using the modified moduli, the residual deformation of the embankment is evaluated. The methodology is applied to two embankments in Japan which suffered severe damage during past earthquakes. The first case study gives a calculated permanent displacement as large as 1.81m, indicating considerable instability of the embankment which actually failed completely. In the second case study, the calculated settlement is 27cm, compared to the observed settlement of 21cm. Therefore, the results of the analyses show reasonably good agreement with the observed deformations of the embankments due to the earthquakes.

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This paper describes an approach for interpreting cone penetration test (CPT) results to provide a direct measure for assessing soil liquefaction potential of fine granular soil deposits. The use of CPT is justified when the cost of conventional testing techniques is high or the quality of soil samples is not satisfactory. The results of a field investigation program conducted in the Mexicali Valley in the north of Mexico were used to develop correlations between, overburden pressure, σ_v', maximum surface acceleration, a_max, and liquefaction potential. The method developed here suggests that CPT data can provide a measure for assessing soil liquefaction potential.

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In recent years, prefabricated vertical strip drains have almost entirely replaced conventional sand drains as the preferred method to speed up the consolidation of soft cohesive soils under preloaded embankment fills. This paper describes an investigation carried out on one of the most important characteristics of vertical drain, longitudinal permeability. The influence of filter jacket and core on the discharge capacity have been investigated. The results shows that the discharge capacity are influenced by the flexibility of filter jacket and the core as well as the geometrical structure of the core. Also the influence is time dependent.

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It is well realized that the in-situ K₀ stress condition of undisturbed soil samples should be reproduced in the laboratory test in order to inspect the mechanical properties of soil properly. In this study, an automatic triaxial testing system was newly developed, in which triaxial tests on undisturbed clay samples after reproducing the in-situ K₀ stress condition can be carried out in a practical manner. According to the results of the tests with this system, it was made clear that the measured K₀-value was largely affected by the compressibility of side drain paper and that the correction was necessary in order to reproduce the in-situ stress condition with the proper K₀-value. The initial isotropic consolidation pressure at which the control of K₀ condition started also had an important effect on the final K₀-value. It is recommended that one sixth or one eighth of the preconsolidation pressure should be used as the initial isotropic consolidation pressure.

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A method is described for expressing the elastic shear modulus of a clay as a power function of the applied pressure and the preconsolidation pressure. The method has the advantage that it incorporates the concept of normalisation of clay properties with respect to pressure, whilst allowing a realistic variation of the shear modulus with overconsolidation ratio to be described. A further advantage is that, since the shear strength is often expressed in a similar manner, the rigidity index G/s_u, which plays an important role in many geotechnical engineering analyses, can be expressed as a power function of the overconsolidation ratio. The new method is compared with some existing data showing the variation of the stiffness of clays.

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