Laterally loaded circular elastic piles in layered soil are analysed by means of a rigorous elastic load transfer theory. In terms of effective stresses, the problem is decomposed into extended soil layers with elastic properties of the layered soil and a fictitious pile characterised by Young's modulus of the real pile and the respective Young's moduli of the soil layers. The unknown fictitious-pile shear force is determined from the condition that the horizontal displacement in the extended soil layers along the centroidal axis of the original pile location caused by a system of interactive forces is equal to the horizontal displacement in the fictitious pile. The real-pile shear force is obtained by combining the fictitious-pile shear force with the areal integral of the effective horizontal shear stress in the extended soil layers at the original pile position. The bending moment on the real pile is obtained from integration of the real pile shear force along the centroidal axis of the pile.Extensive parametric studies with regard to the maximum bending moment and pile top deflection are presented in graphical form for the design and analysis of laterally loaded piles in layered soil.

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Dynamic active earth pressures against rigid retaining structures with dry cohesionless backfill are investigated based on the observations of the shaking table model experiment with different wall movement modes : rotation about the base, rotation about the top, translation and a combination of these. The earth pressure distribution, total dynamic thrust, incremental dynamic thrust and their points of application are discussed in detail. It was found that the dynamic active earth pressure distribution is strongly influenced by the wall movement mode particularly at a low level of horizontal acceleration, while inertial body force effect becomes dominant at a high acceleration level. Soil arching developed near the wall top for rotation about the top mode and high residual stress region near the wall base for rotation about the base mode are significantly attributed to the earth pressure distribution and hence the point of application of active thrust.

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The hardening effect and delay of propagation of pore water pressure were observed in repeated loading test on the specimens of compacted allophaneous volcanic ash soils under undrained condition. These phenomena occurred even in the specimen whose degree of saturation was higher than 95%.This research was carried out to investigate the mechanism of hardening effect of repeated loading on the above highly saturated specimens from the viewpoint on the relation between hardening effect and micro structure. Then, the following results were obtained. (1) The difference of micro structure influenced not only on the behavior of soil in the standard undrained triaxial compression test but also on that in the undrained repeated loading test. (2) Undrained repeated loading had both of hardening and softening effects. (3) The hardening effect was given by the gradual increase in contact area between soil particles, anisotropy and density resulted from deformation and fracture of soil peds and compression of residual micro air bubbles during repeated loading. (4) To obtain the yielding repeated load ratio, the strain ratio (recoverable strain/irrecoverable strain) method was more favorable for allophaneous volcanic ash soils than the strain rate method. The yielding repeated load ratio was 0.4 through all kinds of specimens used in this research.

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The paper presents an analytical model for calculating permanent strains and accumulated pore water pressure due to cyclic loading of saturated sand. The proposed formulation is based on concepts analogous to viscoelasticity to predict strains and pore pressures at the end of one or more cycles of loading without an explicit description of the hysteretic sand behaviour within each cycle. Attention is focused on developing general expressions which also partly account for soil anisotropy and the effect of principal stress rotation. The model parameters are derived empirically from the results of drained or undrained static and cyclic triaxial and simple shear tests. The proposed constitutive equations are incremental, in terms of effective stresses, so that they may be applied to predict permanent strains and accumulated pore water pressure under various drainage and boundary conditions. To illustrate the merits of the proposed formulation, comparisons are presented of computed and recorded response in drained and undrained cyclic triaxial tests, as well as in constant volume cyclic torsional shear tests. The good agreement observed in the comparisons, suggests that the theoretical model, presented here, is a practical alternative to hysteretic stress-strain models for computing permanent strain and accumulated pore pressure.

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Three series of consolidated undrained triaxial compression tests on two saturated remoulded clays were performed to investigate the influence of duration of anisotropic consolidation up to 120 days on the undrained stress-strain behavior of clays.Experimental results show that the initial modulus of deformation and the undrained strength increase with time of consolidation, and the increase in elapsed time of anisotropic consolidation leads to increase the stress level which exerts positive dilatancy at initial stage of shear.A method to predict the undrained shear strength of clay consolidated over a long period of time by applying existing method which has been applied to overconsolidated clay is presented. It is also shown that the method of prediction can be improved by suitable evaluation of the change in dilatancy characteristics of clay with the elapsed time in secondary consolidation.

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The influences of the effective stress change induced by harmonic ocean waves on the stability of sandy submarine sediments in very gently sloped seafloors are examined. The general solution of the problem of flow through poro-elastic media and their deformation is represented by a linear combination of the solution of the Laplace equation and the diffusion equation (consolidation equation). The solution for horizontal seafloors is assumed to be approximately applicable to a very gently sloped planar seafloor. All possible arc failures are found by trial, using the slice method. The geometry of the possible instability is represented by the envelope of all the possible slides.The effective stress changes under the troughs towards the still water level of the storm waves in the direction of wave propagation can cause circular arc failures in sediments with Skempton's pore pressure coefficient, B, of less than 0.8, in water depths down to about 100 m. The length of the largest failure arc is of the order of 1/9∼2/9 of the wavelength, and the length of the composite failure zone can be about 3/4 of the half wavelength. The depths of the slip circle penetration can be of the order of the wave amplitude.

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A constitutive model for sands and clays by which the general strain increments (dε_x, dε_y and dγ_xy) are directly related to the general stress increments (dσ_x, dσ_y and dτ_xy) is proposed. This model is derived from the hyperbolic relationship between the general shear-normal stress ratio (τ_xy/σ_x or τ_xy/σ_y) and the general shear strain (γ_xy), and the "stress-dilatancy relation" expressed in general coordinates. In order to evaluate the influence of rotation of the principal stress axes on strains, "rotation tests", in which the stress path is the circumference of a Mohr's circle, have been carried out by a "two-dimensional general stress apparatus" using a stack of aluminium rods (mixture of φ 1.6 mm and φ 3.0 mm). The test results agree well with the analytical ones based on the proposed model. Simple shear tests and liquefaction tests with rotation of the principal stress axes are also analyzed by the proposed model. The model is extended to a three-dimensional one using the superposition of the "two-dimensional" principal strain increments. The three-dimensional model can analyze all the results of triaxial compression and extension tests under constant mean, major and minor principal stresses, and constant principal stress ratios, and "stress probe" tests in triaxial compression and extension conditions. The stress-strain parameters in the proposed model are determined from a conventional triaxial test and an oedometer test.

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Thick marine clay deposits underlying reclamations have often been treated with vertical drains and surcharge to reduce excessive differential settlements before construction of roads, runways and other structures. Biot's theory of consolidation is implemented, using a 2 D plane strain finite difference scheme, in the solution of the field consolidation problems. To simulate the effect of vertical drains, the soil with drains installed was approximated to a soil with an equivalent increased vertical permeability in a rational manner. The numerical scheme was used to demonstrate the back pressure effect caused by the inflow and backup of excess pore pressure from the untreated clay into the treated zone causing a retardation of consolidation settlement in the latter. A study of the effect of drained-treatment width and surcharge width showed that these parameters significantly affect the rate of consolidation settlement in the treated zone, and therefore it is important to consider these parameters in the design of drains and surcharge in reclamation works.

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Presented is a three-dimensional slope stability analysis which is based on the variational limiting equilibrium approach. The characteristic feature of this approach is the absence of arbitrary assumptions with respect to the shape of the potential slip surface. The analysis is applicable to soil with a homogeneous distribution of material strength parameters. The results are presented in the form of two stability charts. One chart makes it possible to estimate the factor of safety for a given problem and the second enables prediction of the volume of moving soil in case failure does occur. This second chart makes it possible to rationally select the design safety factor where cost of potential repair is considered.The analysis illustrates the importance of the ratio between cohesion and friction in controlling the extent of failure. In particular, it is shown that the factor of safety of purely frictional material stored as a heap is the same as obtained under 2-D configuration.

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A concept to account for the effect of membrane penetration on the generation of pore pressure in liquefaction tests was demonstrated based on experimental studies. The major effect of membrane penetration was to increase the number of cycles to cause liquefaction. The cycle ratio was defined as a ratio between numbers of cycles causing liquefaction with and without compliance at the same stress ratio. The cycle ratio was found to be a unique function of membrane compliance ratio, and independent of applied shear stress. A careful review of the previous study (Martin et al., 1978) yielded the same result, indicating the validity of the concept.Based on the findings, a simplified method was presented for correcting liquefaction test results for the membrane penetration effects. Several previous studies concerning the effects of specimen diameter were used to validate the proposed method, since the resulting difference in the liquefaction strength mainly reflects the membrane penetration effects. The liquefaction strength curves for different diameter specimens after membrane correction were almost coincident, showing a considerable potential of the proposed method.

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A laboratory investigation has been carried out into initial anisotropy and into the effects of continuous principal stress rotation on the undrained behaviour of two granular materials : a natural angular to sub-angular sand and glass ballotini, which comprises spherical grains. Pluviated samples of loose Ham river sand and of ballotini, having the same grading, were isotropically consolidated, then subject to undrained shear in a hollow cylinder apparatus, using a constant b(=(σ₂-σ₃)/(σ₁-σ₃))=0.5. Despite the marked contrast in their grain shapes, both materials displayed stress-strain, strength and pore pressure responses which were strongly dependent on α, the direction of the major principal stress to the vertical during shear.For both materials a surface may be defined in q((σ₁-σ₃)/2)-P'((σ₁'+σ₂'+σ₃')/3)-α space which portrays their undrained initial anisotropy. The surface is shown to be a bounding surface in that it separates possible from impossible states.The bounding surface is capable of anticipating the response of the materials to stress paths involving principal stress rotation, both monotonically and cyclically applied. It distinguishes different patterns of behaviour on the basis of the direction in which principal stresses are rotated and whether effective stress paths travel on or below the surface.The bounding surface is restricted to the stage of undrained shear during which positive pore pressures are generated and levels of octahedral shear strain are, by observation, less than 0.5%.

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Numerical analysis was carried out on earthquake-induced displacement of anchored bulkheads. The permanent displacement of several meters experienced in liquefied areas during the Niigata earthquake was large enough to damage the functions of nearby structures. Since the conventional methods of predicting seismically-induced displacement could not deal with thin sheet-pile walls subject to liquefaction, they were modified and improved. The new method analyzed the limit equilibrium of a backfill soil wedge under the action of pseudostatic seismic force, and calculates the critical acceleration of an earthquake which is required for the sliding mechanism to be activated. By following Newmark's sliding block theory, the seismic acceleration in excess of the critical value is integrated twice with time so that permanent displacement may be obtained. Effects of pore water pressure development is taken into account by allowing the variation of critical acceleration with time. Finally parametric studies were carried out by using the method derived here, and their results are explained briefly.

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The authors proposed a new experimental equation concerning the compressive strength of frozen sands. This equation and its derivative form define the equi-dry specific gravity lines and the equi-degree of saturation lines. These lines were presented in graphical forms and it was understood that : 1) if the degree of saturation is constant, the compressive strength decreases as the water content increases ;2) the water content at which the maximum compressive strength occurs can be quantitatively determined using the dry specific gravity in the densest state.

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Solutions are presented for determination of elastic displacements beneath an optimally designed rectangular foorting subjected to biaxial bending. Linearly varying distribution of loading is assumed in the analysis.

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