The frequency distribution of void ratio was experimentally determined for three actual granular materials having different grain characteristics, i. e., glass beads (spherical grains), Ottawa sand (rounded grains), and Crystal silica sand (angular grains). The distributions were obtained by means of thin sections and a computer-controlled image analyzer. Samples were prepared at different relative densities. The structure of the samples was fixed with epoxy-resin in a specially fabricated mold made of plexiglass. For all samples, the frequency distributions of void ratio were skewed towards the denser void ratios. Further, the distributions for glass beads were not only skewed toward the denser void ratios, but were also very well approximated by the negative exponential distribution. The frequency distribution of both Ottawa and Crystal silica sands was modeled by the beta distribution in this study. The deviation of void ratio was found to increase with both void ratio of the sample and angularity of grains. In addition, it was found that the angle of internal friction was higher for materials composed of angular grains, even though the deviation of void ratio was the greatest in this material.

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Results of model loading tests on dense sand were reviewed to assess the variation in bearing capacity factors N_γ and N_q relative to the width of the foundation base. Consequently, it is confirmed that N_γ decreases non-linearly with increase in the width of foundation base and that N_q decreases more sharply than N_γ does as the width increase. It is also found that N_q decreases as the ratio of burried depth to the width increase. The cause of decrease in N_γ or N_q with increase in the width is regarded to be the rise of stress level which induces lowering of the angle of internal friction φ and volume reduction in the bearing sand by compression.

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Decomposed granite soil which is the residual soil of weathering, is different from so-called transported soil which was transported by river and deposited. Decomposed granite soil has regularity in grain size distribution. Starting from the above finding, in this paper, the weathering process which changes rocks to soil was studied mathematically, and a grading equation was derived. The equation obtained was compared with actual grain size accumulation curves of various types of decomposed granite soil. The equation showed good conformity with the actual condition, and the parameters in the equation were found to be correlated with each other.

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Strength anisotropy and shear band direction at failure and their relationship for sands were studied experimentally. Using reconstituted specimens of air-pluviated Toyoura sand, plane strain compression (PSC) tests, torsional shear tests and a bearing capacity test with a strip surface footing were performed. Also PSC tests were performed using undisturbed specimens of sand taken from layers in the field, formed by secondary deposition under water. For both types of sands, a significant degree of strength anisotropy was observed. For Toyoura sand, shear band(s) did not appear at a unique angle. That is, in the PSC tests on specimens deposited from the σ₁ direction, the bedding plane direction differs largely from the zero-extension direction. In this case, shear bands tended to appear in the direction of the maximum stress obliquity plane. This type of shear band appeared also in a model ground loaded with a smooth footing. On the other hand, in the simple shear tests on specimens deposited vertically, the bedding plane direction coincides with the zero-extension direction (i.e., the horizontal direction). In this case, shear bands tended to appear in the the zero-extension direction. In the other cases, shear bands appeared at intermediate directions. The paper discusses also the point that many of the apparent contradictions concerning the shear band direction reported in the literature may be explained, at least partly, by taking into account the relative direction of bedding plane in each case.

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A practical method for analyzing the load-settlement behaviour of bored cast-in-place plies has been proposed. The method employs Kondner-type hyperbolic load-transfer functions, by which non-linear behaviour can be simulated plainly and simply, for skin resistance and end resistance. The parameters required may be determined from the results of usual in-situ and/or laboratory tests. The procedure for determining the parameters is discussed in detail : It is indicated that displacements needed to mobilize half of the ultimate skin resistance are as small as 1/100 of those of the ultimate end resistance. One-dimensional finite element formulation, which personal computers are enough to solve, for the model proposed is described. Analytical results of loading tests for large-diameter bored piles are discussed. The method proposed may be useful for the following situations : the preliminary analysis for planning an appropriate loading-test program and the back analysis of loading tests for optimizing the design.

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Based on the endochronic theory, constitutive relations for overconsolidated clay subjected to static loading have been obtained. The constitutive relations expressed in a closed form can generally describe both deviatoric shear responses and pore pressure responses including negative responses induced by dilatancy. The model further can account for the effect of effective confining pressure on the responses, strain hardening and softening behaviors, dilatancy behaviors, and the effect of overconsolidated ratio, OCR, on the responses. The model is applied to describe the undrained simple shear test data on Boston Blue clay (Ladd and Foott, 1974) and undrained triaxial compression tests on Shanghai clay as well as South Sea clay carried out by the second author. It is shown in this paper that the model yields a reasonable description for the mechanical behaviors of overconsolidated clays subjected to static loading.

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The behavior of the soft clay grounds subjected to repeated loading is different from that subjected to sustained loading. The difference in settlement between these two loading patterns should be due to secondary compression over a long period of time. Consequently, soft clay grounds subjected to repeated loading tend to be more compressible than those subjected to sustained loading. Therefore, it is necessary for engineers to predict post-construction settlements under repeated loading. In this respect, the preloading is considered to be promising as a countermeasure to reduce the settlement of clay under repeated loading as well as under sustained loading. The effect of preloading on post-construction consolidation settlement of soft clay subjected to repeated loading after removal of a part of preload is investigated in the present paper. It has become clear that the settlement of a clay sample after preconsolidation is mainly affected by the amount of preload, the degree of consolidation due to the preload, the amount of permanent load and the amount of repeated load after removal of preload. The calculated settlement versus time relations using a method to estimate the amount of consolidation settlement of soft clay grounds subjected to repeated loading after removal of preloading were compared with the observed degree of consolidation as parameters of the intensities of preload and repeated load.

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In order to investigate the influence of inherent anisotropy on the yielding and plastic flow of loose and dense sand, a series of experiments involving a wide range of principal stress axes directions were carried out on hollow cylindrical specimens of Toyoura sand using a torsional shear test apparatus. Stress paths involving cycles of stress reversal and stress axis rotation were performed in order to identify the states of stress at which plastic flow begins to take place. The test results revealed well-defined families of yield loci having identical shapes in the stress space independent of the density of sand. Experimental evidence presented here shows that the direction of the plastic strains for different stress increments is not uniquely established indicating the non-existence of a unique plastic potential. Consequently, within the framework of conventional theory of plasticity, the yielding and flow of sand can only be explained with the concept of multiple yield surfaces.

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Of several triggering mechanisms of submarine slope instability, the effect of rapid rate of sedimentation is focused on. When subjected to rapid sedimentation, the clayey material in the seabed is in a state of incomplete consolidation or underconsolidation. In order to understand the undrained behaviour of underconsolidated clay, triaxial compression tests were conducted on laboratory-reconstituted samples of soft Bangkok clay which were consolidated under various total pressures and degrees of consolidation. The test results indicated that the undrained strength of the clay increases with the degree of consolidation, while the cohesion and friction angle in terms of effective stress are independent of the degree of consolidation. It was revealed also that the underconsolidated clay develops a slightly greater amount of excess pore water pressure during shear than the normally consolidated clay. Using the above findings, a finite element program was developed to analyze the stability of submarine slopes undergoing rapid sedimentation and increasing height with time. It was shown by an example calculation that the degree of consolidation of the slope decreases with time, eventually resulting in a failure.

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This paper reports a series of laboratory tests on sand-concrete friction under two-way repeated loading with a simple shear type apparatus. Under monotonic loading, the tangential displacement mostly consists of the shear deformation of sand mass before the yielding of interfaces. After the yielding, the interface sliding becomes the major factor of tangential displacement. The maximum coefficient of sand-concrete friction depends on the surface roughness of concrete and the mean diameter of sand. These effects are combined into the influence of Normalized Roughness of the interfaces. The shear strength of sand affects the upper limit to the coefficient of friction. The residual coefficient of friction under two-way repeated loading coincides with that under monotonic loading. A shear zone forms along a sand-concrete interface during the sliding. Shear zone formation explains the reduction of upper limit to the coefficient of friction. These characteristics of sand-concrete friction are similar to those of friction between sand and rough steel surfaces.

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Shear strength and consolidation yielding stress of heavily overconsolidated Pleistocene clay found at Izumi-hill of Osaka District are presented. Unconfined compression, field vane and various kinds of direct shear tests were conducted for evaluating the shear strength, while standard and strain controlled oedometer tests were carried out for determining the consolidation yielding stress. It was found that unconfined compressive strength is about half of field vane and direct shear strengths, and this difference was suggested to be caused by that extensive failure at a weak point takes place in most case in unconfined compression test. It was also found that field vane test is an effective tool for evaluating the shear strength of this kind of material. Consolidation yielding stress determined by standard and strain controlled oedometer tests are discussed as related to the undrained shear strength obtained from direct shear test. It was strongly suggested that the consolidation yielding stress should be determined by strain controlled oedometer test and the clay investigated is fundamentally classified into normally consolidated aged clay.

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A constitutive model for soils by which the strain increments (dε_x, dε_y and dγ_xy) are directly related to the stress increments (dσ_x, dσ_y and dτ_xy) is proposed. The stress-strain matrix between the strain increments and the stress increments is expressed in xy-coordinates fixed arbitrarily. In order to evaluate the influence of rotation of the principal stress axes on strains, "principal stress rotation tests" with several rotation times, in which the stress path circles several times along the circumference of a Mohr's stress circle, are carried out by a "two-dimensional arbitrary stress apparatus" using a stack of aluminiulm rods. The "arbitrary" stress path dependency of strains is also examined by the same apparatus, and analyzed by the proposed model. The finite element analysis of soil foundation under a uniform strip load is performed using the proposed model, and the influence of rotation of the principal stress axes on settlements and lateral displacements is checked by comparing the computed results under different contribution factors (5% to 100%) of strains due to rotation of the principal stress axes. It is seen from the computed results that the settlements and lateral displacements are influenced significantly by the principal stress rotation.

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The validity of the stress dilatancy equation for representing the small stress ratio state response of sand is examined. Test equipment development and procedures that were followed aimed at precise loading control and reliable monitoring of small displacements and volume changes. A variety of load controlled stress paths were applied to conventional triaxial test samples of Ottawa sand. The results obtained show that at small stress ratio states a relationship between stress state and strain increment direction as prescribed by the stress dilatancy equation does not apply. Stress increment directions were found to be related to strain increment directions for low stress ratio states. The relationship has some resemblance to the behavior of a cross anisotropic elastic material with a stiffer vertical to radial response. The range of low stress ratio states over which a stress dilatancy relationship does not apply tends to increase with density. In stress ratio regions where the stress dilatancy equation began to apply, the relationship between R and D tends toward K_CV with increasing confining stress for conventional triaxial but not for constant mean normal stress paths.

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Using the method of characteristics, for soils with nonhomogeneity in angle of internal friction mobilized, contours of angle of internal friction mobilized and stability numbers are obtained. Stability numbers obtained give higher values of factor of safety when compared to Taylor's values.

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The classical theory of isotropic elasiticity has been extensively used for estimating stresses developed in loaded soil mass, because of its simplicity. Natural soils and rocks, however, exibit essentially anisotropic nature. The first author, therefore, has derived basic anisotropic stress formulae in which stress distribution is controlled by just a single parameter of Young's modulus ratio, n. Recently, artificial earth reinforcing members are inserted horizontally into the weak soils. This brings the foundation more anisotropic than the original and yields a higher horizontal rigidity. Thus the authors suppose to apply his solutions to this kind of problem. In this note, the stresses generated due to strip, triangular and embankment loading are obtained. The pressure bulbs are drawn to illustrate the load spreading capacity of anisotropic foundation. For engineer's help, influence chart of vertical stresses due to embankment loading is prepared in a style of Osterburg's for various values of n.

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