A comprehensive series of triaxial compression tests was carried out on undisturbed samples of Weathered Bangkok Clay. These tests included (i) anisotropic consolidation under different stress ratios (ii) undrained tests and (iii) drained tests.A yield locus for volumetric strain is established for the Weathered Clay which separates the states for which the volumetric strain is small from those for which the volumetric strain is large. The strain paths followed during anisotropic consolidation are made up of two straight lines with different slopes. One corresponds to the case inside the yield locus and the other corresponds to the case outside. (dυ/dε)-η vs η relationships are found to be different for both cases.From a series of undrained tests carried out on samples consolidated to pre-shear consolidation pressures less than the maximum past pressure, the effective stress paths in (q, p) plot are found to be approximately parallel to the q-axis and the constant shear strain contours are found to be nearly parallel to the p-axis. The results of undrained and fully drained tests on Weathered Clay consolidated to the normally consolidated states are presented and discussed.

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This paper describes (1) the general characteristics of quick sand, (2) a method for the determination of the undrained strength of a quick sand which is located in the Arabian Gulf and (3) an example of a stability analysis of a structure constructed on this quick sand deposit.From a brief review on past studies on quick sand, it is first shown that the quick sand possesses quite different shear characteristics from the usual type of sand and is characterized by a liquefaction type failure under static shear conditions. From an examination of consolidated undrained strength tests performed on undisturbed and disturbed samples of a quick sand located in the Arabian Gulf, it is then shown that the undrained strength of this quick sand is almost the same as that of normally consolidated clay and that anisotropy in undrained strength is relatively greater than that of clay. Finally the results of a stability analysis for sliding of a structure (a rubble-mound breakwater) is shown. The analysis used undrained strength values for the quick sand and considered the effect of anisotropy in the undrained strength.

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The lateral pressure transmittal through different types of backfill material; characterized through a material parameter E/G; subjected to different types of contact pressure on its surface is evaluated theoretically by the use of the concept, in which it is considered that E/G>2(1+ν). The backfill material extending upto infinity depth as well as limited by the presence of rigid boundaries having different frictional characteristics have been considered. The physical and mechanical characteristics of the granular materials affecting the development of lateral pressures on retaining wall are investigated. The model used in the analysis is found to be applicable to a wide range of materials ranging from solid like at one end to liquid like at the other end.Qualitative numerical results over a wide range of the values of the material parameter (E/G) have been presented in a non-dimensional form to elucidate its influence on this problem. The results are also compared with that of Boussinesq's approach. It is observed that the softer/looser the backfill, the poorer is pressure transmission in horizontal direction resulting in a overall decrease of the lateral pressure on the retaining structure. The proposed model gives a partial explanation of the divergences between the results of the existing theories and reality.

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Dynamic material properties of soil needed for the nonlinear analysis of earthquake response of the ground have usually been measured in the laboratory using the torsional column shear device. The cyclic triaxial test, despite its easier accessibility and handling for practicing engineers, has seldom been looked upon as a rational way to make a reliable measurement of dynamic properties. In this experimental study a highly sensitive gap sensor and a sealed load transducer are introduced inside the triaxial cell to eliminate the frictions of the conventional displacement sensor and the loading piston. A series of cyclic triaxial tests featuring these improvements have been carried out for saturated Toyoura sand with various void ratios and confining pressures, disclosing the following facts.(i) Reliable measurements of the shear modulus and its strain dependent variation within a wide strain range of the order of 10^-6 to 10^-3 are possible with the improved cyclic loading test, permitting a direct connection with the insitu shear wave velocity.(ii) An essentially good agreement of the modulus is quantitatively recognizable between the triaxial test and the torsional shear test, implying that the different stress and confining conditions inherent to the individual testing devices give no significant effect on the evaluation of the modulus.(iii) This test gives a reasonable hysteretic damping ratio as well as its strain dependency although the damping ratios measured by other researchers with different testing devices widely differ from each other indicating the difficulties for evaluating accurate damping ratio.

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The settling behavior of dilute clay-water mixtures is examined. At first, settling type is classified into the four based on the precise observation of settling phenomena. Two factors are considered to cause the difference in the settling type; one is the degree of flocculation which is determined by salt concentration in water and the other is the degree of particle's interaction which is determined by mixture's solid concentration. Two of the four settling types, i.e., zone settling and consolidation settling, are nextly examined from the quantitative view point. The results show that settling is strongly influenced by the total solid weight contained in a mixture.

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In order to predict the consolidation constants for very soft soils with high water contents, the constant rate of strain consolidation test method has been proposed together with a new interpretation of the test results. Three kinds of diagrams are constructed on the basis of the finite difference solutions for the basic equation of consolidation including the large strain effects. It has been found that using such diagrams, the consolidation constants of very soft clays in the pressure range required for practice can be accurately determined from consolidation tests under constant rates of strain.

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Following the Miyagiken-oki earthquake of June 12, 1978, signs of considerable liquefaction were observed over the reclaimed sand deposit in the area of Ishinomaki fishery port. Three oil storage tanks constructed in thin area but on the deposit compacted survived without any damage notwith-standing the considerable liquefaction that had developed in the surrounding area. After the earthquake, undisturbed sand samples were taken by means of Osterberg piston sampler both from the compacted deposit and from the uncompacted deposit. Laboratory cyclic triaxial shear tests were performed on these specimens to determine the in-situ cyclic strengths of the sands. The cyclic strengths thus determined were incorporated into a simple analysis to determine the potential for liquefaction in these two deposits. The results of the liquefaction analysis were discussed in the light of the construction record and the observed performances of the tanks and deposits during the 1978 earthquake.

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Based on the fundamental experimental properties, the author presents a new theory of plastic shear deformation of granular materials. The theory involves (a) yield function, (b) plastic potential, (c) stability condition and (d) deformation rule. The yield function is defined by the author's new state function S_s. The plastic potential μis provided for the drained shear and the undrained shear. The stability condition can uniquely classify a experimental stress path into 'stable yielding' or 'unstable yielding' in terms of the functions of S_s and μ.

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