Mudflows, debris flows and solifluction sheets are shallow instability forms with a distinct texture, this being a mixture of clay or rock lumps and a soft matrix of mud. The general equations of a new approach, previously introduced in a limited version, designed to calculate the stability of this type of mixture when located on a slope are presented. The new approach takes into consideration the particulate structure of the mixture as well as the shear strength provided by the lumps and the muddy matrix. Using the new approach, the least slope angles at which two reported mudflows got mobilized in the field were predicted well.

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A model introduced in the present paper is capable of describing the mechanical behaviour of anisotropically consolidated clay reasonably well. The salient features of the proposed model are summarized as follows : (i) Generalized forms of the Cambridge models are given to both yield function and plastic potential. (ii) A combination of isotropic and kinematic hardening is used. (iii) A non-associate flow rule is proposed. (iv) The isotropic hardening involves plastic work related to not only volumetric but also deviatoric deformation. (v) The translation of yield surface is specified by extending Ziegler's rule of kinematic hardening. (vi) The constitutive model is capable of describing expansion of yield surface with simultaneous translation in the stress space. Several undrained triaxial tests of anisotropically consolidated clay are simulated and the good agreement is observed between simulation and experimental data.

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The dynamic characteristics of embedded rigid foundations are studied using the boundary element method. Lateral dashpots are introduced to the soil in plane strain in order to represent the wave propagation toward the third direction from a slice of the soil and their effects are examined. The impedance functions and foundation input motions are presented for the case of a rigid foundation embedded in a half-space or a stratum and for the case of two rigid foundations also embedded in a half-space. The effect of the lateral dashpots on the soil-structure interaction is studied where the embedment, the bedrock and the adjacent foundation are considered. The numerical examples are provided by comparing the results obtained by two-dimensional, approximate three-dimensional and exact three-dimensional analyses. The efficiency of the dashpots is confirmed, in particular, for a foundation embedded in a half-space. Based on this result, the lateral dashpots are introduced to one-dimensional soil columns which represent a half-space around an embedded foundation. From this assumption, the impedance functions are easily obtained in an explicit form and the foundation input motions are evaluated using the substructure technique. The validity of this simplified technique is confirmed by comparing its results with those obtained by a three-dimensional boundary element analysis.

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In order to simulate the formation of localized shear bands, which is commonly observed during large deformation of soils, we first present a systematic extension of the well known Cam-clay model developed for small strains to the model for finite strains/deformations and then incorporates a non-coaxial term in the model. Finally, confining the deformation to undrained plane strain conditions, we examine the effects of the non-coaxial term on the shear bands formation.

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A constitutive model of natural soft clay with strain softening, which is an important feature of overconsolidated clay, has been developed based on the concept of elasto-plasticity with memory. A new stress history tensor, which denotes a memory of stress with respect to strain, has been introduced by use of a strain measure. The stress history tensor is effective for discribing the deformation feature of frictional materials with strain softening. By using this stress history tensor, we extend the elasto-plasticity theory of overconsolidated clays previously proposed by Oka et al. The proposed model is capable of describing the strain-hardening and strain-softening behavior of natural soft clays in the overconsolidated region, and was applied to the triaxial drained and undrained behavior of a Champlain sea clay from eastern Canada. The comparison between volumetric and axial strain responses of experiment and simulation shows good agreement.

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The mechanical properties, in particular, the dynamic deformation properties of sedimentary soft rocks which were artificially weathered through dry-wet and freeze-thaw sequence are determined by cyclic triaxial tests and ultrasonic pulse tests in the laboratory. First, the relations among unconfined compressive strength q_u, Young's modulus E by uniaxial compression tests, and shear wave velocity V_s by ultrasonic pulse tests are investigated, and it is shown that probable values of q_u and E of weathered soft rocks can be estimated from V_s. Also, it is concluded from cyclic triaxial tests that (1) the greater the extent of weathering, the larger becomes the dependency on confining pressure of shear modulus G_o at very small strain, (2) relations between shear modulus ratio G/G_o and shear strain amplitude γ depend on the extent of weathering, namely the degree of degradation of G/G_o with γ of heavily weathered specimens is smaller than that of fresh samples. However, if γ is normalized with respect to the reference strain γ_r, G/G_o versus γ/γ_r relations are uniquely expressed irrespective of the degree of weathering, (3) moreover, material damping h versus γ/γ_r relations are also uniquely defined, (4) relations between V_s and γ_r are given as linear on log-log scaled paper, and the larger the shear wave velocity V_s, the smaller becomes the reference strain γ_r. While this relation slightly depends on kind of materials and magnitude of confining pressure, the probable values of γ_r which have a significant influence on the strain dependency of G and h may be estimated from V_s.

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The contact pressure distributions obtained in tests with "rigid" footings on a cohesionless sand base, are reviewed first. Whereas in the tests, conducted with relatively small stamps and large loads the recorded pressures were parabolic with a maximum value at the center, tests for larger footings, subjected to loads that are smaller than the bearing capacity, revealed that the distribution is saddle-shaped. This distribution leads to higher bending moments in the footings, than predicted by the common assumption that the pressure is uniform. A method is then proposed to take these findings into consideration, by introducing the observed edge-layer effect into analyses that utilize foundation models. The method is demonstrated on two examples. Paper concludes by comparing the obtained solutions with corresponding test results. It is shown that the proposed method leads to a solution that contains the essential features recorded in tests with footings on a sand base.

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In many soil-structure interaction problems, such as reinforced soils, the effect of restrained dilatancy in the interface between the soil and the inclusion plays an important role. In this paper, the restrained dilatancy behavior of an interface is first outlined. A bilinear relation between the shear stress and the shear displacement and a bilinear relation between the increase in normal stress due to shearing and the shear displacement are proposed to idealize such restrained dilatancy characteristics. A model of dilatant joint element is proposed on the basis of simple elastoplastic theory. The response of the elastoplastic joint element under the restrained dilatancy effect becomes prime concern. Therefore, the proposed elastoplastic joint element is analytically examined by a restrained direct shear test of an interface. It is found that our proposed model can represent very successfully the fundamental characteristics of the restrained dilatancy in the interface. Applications of the joint element to the finite element analysis of a field loading and excavation test on a cut slope reinforced by tensile inclusions demonstrate in success the applicability of the proposed elastoplastic joint element to the practical reinforced slope stability problems.

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Presented is a method for analyzing the end-of-construction stability of a granular embankment over a clayey foundation with a variable undrained strength. The mechanism utilized allows the embankment to "break" steeply squeezing out the clay underneath. By virtue of the mechanism used, the factor of safety can be determined through a simple minimization process and without resorting to statical assumptions. The formulation is presented in a framework of limit-equilibrium ; however, its results can also be shown in the context of limit-analysis. To demonstrate the method's performance, some results are presented. The factor of safety predictions compare well with those obtained from Spencer's method. Also, stability analysis predictions compare reasonably well with a field case history.

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The distributions of slippage, normal stress and shear resistance occurred on the interface between track belt with grousers and terrain should be analysed in detail to determine the traffic performance of tracked vehicle running on a weak terrain. Here, on the basis of track model test results, those distributions under rigid tracked vehicle with regular triangular type grousers running on a super weak marine sediment are analysed theoretically at driving and braking state. It is clarified that, at driving state, the amount of slippage under the track belt is positive and increases linearly to the rear end, and the normal stress and the shear resistance on the bottom-dead-center of frontidler become larger than those of rear sprocket with the increment of slip ratio due to the decreasing eccentricity. And at braking state, the amount of slippage and the shear resistance change from positive values to negative ones at some point on the main straight part of track belt or on the contact part of frontidler due to the slip ratio, while the distribution of normal stress is almost invariable with slip ratio.

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Friction between sand and steel is studied by laboratory tests under repeated loading. The interface behavior under one-way and two-way repeated loading was compared with the behavior under monotonic loading. Once a sand-steel interface slides, the coefficient of friction at the re-start of sliding becomes different from the peak value in the first. The coefficient of friction under repeated loading converges to a value close to the residual shear stress ratio of the sand mass. A shear zone formation along sand-steel interface was observed with macroscopic photographing. This shear zone formation along the sand-steel interface explains the decrease of upper-limiting value of the coefficient of friction. The amount of particle crushing was evaluated by sieving the sand before and after the friction tests. Particle crushing explains the influence of sand type and normal stress in the increase of the coefficient of friction under repeated loading.

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Laboratory model test results for the holding capacity of inclined shallow square plate anchors in clay (φ=0 concept) have been presented. The inclination of the anchor with respect to the horizontal was varied from zero to 90°. Based on the model study, an empirical relationship for estimating the ultimate holding capacity of the anchors has been presented.

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To investigate the undrained shear strength anisotropy of K₀-consolidated cohesive soils, undrained triaxial compression and extension tests with K₀-consolidated and K₀-rebound were performed on two kinds of cohesive soils. As a result, the undrained shear strength anisotropy is approximately constant within the range of OCRs of 1 to 10. The reason for this may be considered that the inherent structual anisotropy in a soil specimen produced during initial K₀-consolidation history before rebound is essentially maintained during swelling. The constant undrained shear strength anisotropy, however, seems to depend on the amount of clay fraction and plasticity index of the soils.

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The note presents an analytical solution for evaluating permanent displacement in dynamic problems modelled by Newmark's sliding block. Mono-pulse or cyclic loads can be easily treated. In the case of several pulse loads, the equation enables the interaction between the pulses to be analyzed. For seismic input, the solution can also be conveniently used if the critical acceleration is exceeded by a few of the pulses only.

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Cyclic torsional shear tests on hollow cylindrical specimens were conducted to investigate the effects of degree of saturation on the undrained cyclic shear strength (liquefaction resistance) of air-pluviated Toyoura sand at a relative density of 60 percent. The tests showed that (1) the liquefaction resistance increased significantly with a decrease in degree of saturation to such an extent that the liquefaction resistance at 70 percent saturation was about three times that at full saturation ; (2) the liquefaction resistance also increased with a decrease in B-value, although a near-zero B-value was required for a significant increase in the liquefaction resistance; and (3) the cyclic shear behavior of the partially saturated sand resembled that of denser saturated sand, exhibiting high strength as well as stable deformation characteristics. Based on the above findings it is concluded that a reduction in degree of saturation can be an effective means to increase the liquefaction resistance of loose sands.

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An experimental investigation was carried out to study the effect of embedment and load eccentricity on the depth of the rupture surface beneath footings loaded to failure. A stereophotogrammetric method was utilized to determine the rupture surfaces in a series of model footing tests in which the depth of embedment and the load eccentricity were varied. The results were interpreted and a procedure for computing the depth of the rupture surface is proposed. The parameters involved in this computation are the width and the embedment of the footing, the inclination and eccentricity of the load and the friction angle of the soil.

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