Within the framework of certain concepts presented nearly two decades ago a constitutive law for sand is established which is capable of describing the mode of deformation experienced during quite complicated loading paths of the generalized stress space. The proposed law assumes the existance of a yield surface and a bounding surface and as such is a two surface model. It is a consistent isotropic-kinematic hardening law which, in view of its general nature, can be readily incorporated in a suitable numerical code ; the finite element code for example. The paper provides a detailed mathematical formulation concerning the virgin loading process as well as stress-reversal histories during which the stress paths penetrates the interior of the bounding surface. The formulation is based on the theory of plasticity incorporating a non-associated flow rule and the concept of reflected plastic potential. The mathematical description is followed by a discussion concerning the performance of the model. In particular, the concept is applied to simulate a number of complex 'triaxial' loading programs carried out on a typical granular medium. The emphasis is placed on modelling of liquefaction and cyclic mobility phenomena. For a number of tests, the performance of the model is compared with experimental results. The predictions, although restricted to triaxial configuration only, are quite encouraging and indicate that the applicability of the model extends to a quite wide spectrum of initial void ratios, ranging from a very loose sand to a very dense one.

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Response spectra of strong earthquake ground motions have been known to be influenced by many factors-source mechanism, propagation path of earthquake waves and local soil conditions. In order to clarify the effects of these factors on response spectra, the present paper deals with a statistical analysis of the response spectra of strong-motion earthquake records obtained in Japan. A new multiple regression technique, in which not only the earthquake factors but also the local site conditions are employed as its independent variables, is carried out and an empirical expression for scaling the response spectra is derived. In addition to scaling the response spectra on the bed rock in terms of earthquake magnitude, hypocentral depth and epicentral distance, the effects of the local site conditions on the response spectra are estimated quantitatively as amplification factors of spectra. It is shown that the amplification factors of spectra depend significantly on the local soil layer conditions, and they agree comparatively well with the theoretical amplification factors to the vertical indicence of S-wave. Also, the statistical model presented here is confirmed to be an effective tool for predicting response spectra provided that earthquake factors and site soil conditions are available.

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Series of laboratory tests are crried out on the friction between steel and air-dried sands with a simple shear apparatus. The significance of factors on the frictional coefficient are examined with the use of the experimental design method by orthogonal array table. The influence of sand type (Fujigawa Sand, Fukushima Sand, Toyoura Sand and Glass Beads) and the surface roughness of steel (R_max=1.5∼3 μm and 10∼15 μm) are found to be significant, while the effects of normal stress (98 kPa and 980 kPa) and mean grain size (0.55∼0.62 mm and 0.15∼0.19 mm) are of poor significance. The sliding displacement at the contact surface and the displacement due to shear deformation of sand mass were obtained distinctively. The shear deformation of sand mass was found to be unaffected by the surface roughness of the steel.

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In this research an attempt is made to derive the following two approaches of arithmetic methods of evaluating ultimate bearing capacity of normally consolidated clay foundation subject to partial loading such as embankment with finite width. The two approaches are as follows : (1) Finite element deformation analysis of elasto-plastic clay foundation including consolidation behavior, and(2) Limit state analysis by rigid plastic finite element method.In the former analysis, the stiffness factor of clay foundation in terms of effective stresses is newly introduced, from which the definition of total failure of clay foundation is freshly made. In the latter analysis, stress induced anisotropy of undrained shear strength of clay is newly introduced so that the consistency be held between the limit analysis and load deformation analysis.Main conclusions obtained in the present study are as follows : (1) The solution of rigid plastic finite element analysis is shown to be very close to the solution obtained in a deformation analysis as far as undrained condition is concerned.(2) The effect of partial drainage expected during gradual load application is found to be less than 30% of undrained bearing capacity when the loading rate is within the range commonly used in engineering practice.

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This paper investigates the practical use of the back-analysis through the trial applications of the analysis to six test embankment projects on soft clay deposits. The method of back-analysis previously proposed by the authors, estimates the Young's modulus, the Poisson's ratio and the permeability in multiple soil layers from the monitored movements of subsoil under consolidation. At first, the back-analyzed soil parameters are compared with the ones obtained from the results of laboratory tests. For instance, the 10 times value of permeability estimated from the oedometer tests gives a good approximation to the back-analyzed permeability. However, there is no clear relationship between the back-analyzed Young's modulus and the one estimated from the laboratory test results. Secondly, the changes in soil parameters during the consolidation are studied by use of the soil parameters back-analyzed at the several stages of construction. For example, the decrease in deformation moduli with the progress of consolidation can be well represented by employing the hyperbolic stress-strain relationship. Thirdly, the possibility of applying the back-analysis to the observational procedure in construction phase is shown using the trend of changes in soil parameters during the consolidation.

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Methods of predicting the cyclic undrained strengths of normally consolidated saturated reconstituted sand subjected to irregular loadings from those subjected to uniform loadings are discussed based on the results of torsional shear tests on hollow cylindrical specimens of two kinds of sands. Two time histories of acceleration at the ground surface during earthquakes were used as input irregular loading patterns. A new method to account for the difference in liquefaction strength between uniform and irregular loadings is proposed. In this method, the liquefaction strength against uniform loading is represented by the critical number of loading cycles (N_c)_cr. (N_c)_cr is defined as the number of loading cycles at which the strength curve representing the relationship between the cyclic stress ratio and the logarithm of the numver of cycles N_c to liquefaction has the maximum curvature. It was found that the liquefaction strength against a given irregular loading pattern represented by the maximum single amplitude of cyclic shear stress is a linear function of the logarithm of (N_c)_cr, whereas the slope depends on the wave form. Furthermore, the cumulative damage concept was found useful to predict whether or not a given sand element fails against a given time history of cyclic shear stress series when the strength curve for uniform loadings is given for this element.

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Measurements made of the changing stress state during a constant volume simple shear test on kaolin permit the implied pore pressure change to be divided into a component due to change in total mean stress and a component due to dilatancy of the soil.

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The Matsuoka-Nakai failure criterion for a frictional material, and the Von Mises criterion for a cohesive material are expressed in such a way that they are seen to bear similar relationships to the cohesionless Mohr-Coulomb and Tresca criteria respectively. A generalisation of the Matsuoka-Nakai and Von Mises criteria for materials with friction and cohesion is described, which bears a similar relationship to the general Mohr-Coulomb criterion. The new criterion is expressed conveniently in terms of principal stresses, and is also expressed in terms of stress invariants.

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