Anisotropic stresses may induce anisotropic permeability of rocks. The present study aims at establishing the relation between permeability tensor and principal stresses for Shirahama sandstone within the pre-yield range. The effects of three principal stresses on the permeability are experimentally investigated using a Mogi-type true triaxial apparatus and transient pulse technique. Stress sensitivity coefficients of permeability are defined to describe the influence coefficients of stresses, which are found to be independent of stress states and loading paths. Based on these observations, we proposed a linear relation between the logarithm of the principal components of permeability tensor and the principal stresses.

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The stability of a rock slope beside the Root 45, which has been qualitatively judged as “a dangerous slope” by many experts of the Ministry of Construction of Japan, is quantitatively evaluated by the analysis method that has already been proposed by the authors based on the homogenization theory, and the validity of the proposed analysis method is examined. In the analysis only graphical image of crack pattern and the mechanical properties of intact rocks consisting of the rock mass are used. The results analyzed show rather good evaluation for the “dangerous state” of the rock slope, and the validity and applicability of the method is confirmed.

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In constructed the pre-cast tunnel structures, it assumed that the earth pressure acting on the tunnel lining is larger than the overburden pressure and the bending moment becomes increasing. In particular, in case of higher overburden, tunnel lining must be became heavy thickness so as to support the large earth pressures. This is the reason why the pre-cast tunnel structures are mainly used in the shallow overburden tunnels. In this paper, performing two dimensional trap door tests using by the aluminum rods layer, the earth pressure and the bending moment on the pre-cast tunnel lining models are measured in consideration of the constructed process. Then, to introduce the lower stiff material around the tunnel lining, the effect of the lower stiff material are verified. Based on the experimental results, it is found that the earth pressures acting on the tunnel lining can be decreased to applying the lower stiff material.

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In failure problem of soil, localization of deformation, progressive failure and unstable failure is dominated. Those phenomena affect peak load and post-peak behavior. In this research, we direct our attention to unstable failure and suggest a condition for beginning of unstable failure by using J-integral. As a result of finite element analysis which is applied for the suggested condition, we can reproduce different failure phenomena for rock shear test in various vertical load. And it is shown we can reproduce an unstable failure in rock shear test and progressive failure test.

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In order to investigate an effect of stress history on K₀ value and a change in undrained shear strength which caused by secondary consolidation during K₀ condition, triaxial compression tests using undisturbed marine clay were carried out by using an automatic control equipment. Results from laboratory K₀ consolidated undrained shear test could be summarized as, 1) K₀ value would be strongly affected by clay structure which depend on ageing effects chemical cementation and be subject to stress history. 2) K₀ value would be kept constant during secondary consolidation. 3) A unique effective stress path was showed due to the effect of dilatancy properties and softening stress-strain relationship during secondary consolidation. 4) q_max and E₅₀ would be increasing in proportional to consolidated elapsed time on scale of logarithm before reaching to C. S. L line, and they would be independent of the time after reaching the C. S. L line. 5) q_max was located in an inherence line in p′-q plane. 6) It is possible that q_max could be estimated by a simple function based on the test results.

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A series of triaxial compression test was conducted to examine characteristics in mechanical behaviour of reconstituted clay. The drained shearing under conditions of constant mean effective stress was applied to samples subjected to isotropic over-consolidation history resulting in the O. C. R. ranging from 0 to 2, and also to samples experienced by drained pre-shearing histories. An undrained test on isotropic normally consolidated sample was also conducted. It is clearly demonstrated that the void ratio was not the unique function of the mean effective stress and principal stress difference. Alternatively, a newly proposed strain parameter; i. e., areal strain on the plane being normal to σ₃-axis, is the unique function of these stress parameters.

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In this study, column tests were carried out to measure the coefficients of molecular diffusion of high plastic kaolin clay with different void ratios and numerical analyses were conducted to estimate the accuracy of the measured dispersion coefficients. The result of column tests showed that hydrodynamic dispersion in the clay was mainly caused by the molecular diffusion and the trend between the void ratio and the dispersion coefficients was similar to that between void ratio and hydraulic conductivity. From the numerical analyses, it was found that the precision of measurement of dispersion coefficients depended on the vertical distributions of physical properties of clay sample and the accuracy of the initial and boundary condition in column tests.

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The patterns of failure in a pull-out test are visualized by X-ray CT scanner to supply the basic data on the bond failure of rock bolt and cable bolt. In the pull-out test, a comparison was made between two types of cable bolts and rock bolts. From the results, it is shown that the microscopic failure mechanism is classified as the different failure mode. Then the supporting effect of rock bolts and cable bolts are discussed.

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A new model with double loading functions, one for compressive deformation and the other for shear deformation by Hyperbolic function, is proposed. Validity of this model was tested by analyzing results of bearing capacity model experiments on sand in a centrifuge under accelerations of 20, 40, 60 and 80g. It was found that loading stresssettlement relationships of the experiments were predicted using the model with slight differences. In addition, the scale effect observed in the experiments was simulated using the model. However, the stress distributions underneath the footing computed by employing the model did not coincide with that of the experiment under 40g due to ignoring softening in the model. Accuracy of the Duncan-Chang model and a single loading model were also tested. It was found that neither model was appropriate to describe the test results.

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This paper deals with the method of characteristics established as a direct method of solving cone resistance in c-φ soil. The bearing capacity of cones was analyzed under the condition of axial-symmetry obeying the Mohr-Coulomb failure criterion, considering cone roughness and the intermediate principal stress. The results of the analysis are represented in contour of the bearing capacity related to both cohesion and friction angle. In this paper, as an application of the theoretical analysis, an idea for estimating c and φ simultaneously by using two types of cone which has different tip angle was proposed.

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The compacted bentonite and sand-bentonite mixture are attracting greater attention as buffer and backfill materials for high-level nuclear wastes disposal because they have impermeable and swelling properties. This study investigated the hydraulic-conductivities at the different sand-bentonite mass ratio and dry density, which are the specifications of material, by the experimental works. This study also obtained the experimental data of hydraulic conductivities of the materials for 120 days at the farthest, and the permeability changes before and after swelling. Furthermore, this study proposed the evaluation method for hydraulic conductivity using the parameter “Swelling volumetric strain of montmorillonite”, which was proposed by the authors.

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Hydraulic fracturing stress measurements cannot provide the magnitude of maximum compressive stress with sufficient reliability. To overcome the defect, a new loading probe that can generate a fracture plane in any desirable direction, was developed. The authors examined a borehole wall stress condition induced by the probe and simulated a pressure-displacement curve using a boundary element method. The laboratory experiments provided apparent acceptable results, however, this investigation elucidated that the results come from the fact that ignoring twice large stress concentration at a crack position was canceled out by misreading a re-opening pressure twice large. Thus, it was found that establishment of a method to determine a correct re-opening pressure is essential to make this

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In order to clarify the influence of confining stress, void ratio and particle breakage on the dynamic deformation characteristics of volcanic soils, some site investigations (e. g. standard penetration test and seismic cone penetration test) and cyclic undrained triaxial tests on undisturbed and reconstituted samples were carried out. The test results showed that the effect of confining stress on shear modulus G for crushable volcanic soils is more remarkable than Toyoura sand. However, confining stress-dependency of damping ratio h for crushable volcanic soils becomes less pronounced. Also, G values of crushable volcanic soils, consisting mainly of brittle pumice, are less dependent on void ratio than sand and Shirasu. Moreover, cementation effect in the volcanic ground on the dynamic properties for small strain level was detailedly discussed.

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An elaborate triaxial testing system has been newly developed to investigate deformation of clay over a wide strain range in the laboratory. In this system, a digital servo-motor having a high-resolution is driven by a personal-computer by which the axial deformation as well as the axial stress acting on the clay specimen can be altered with time over a wide range of strain rate. Since the control of confirming pressure as well as the data acquisition is also fully automated, the capability of this triaxial testing system is grossly enhanced by enabling us to perform a wide range of tests such as K₀-consolidation, monotonic compression/extension tests (strength tests), cyclic deformation test etc in a single apparatus. In this paper, the hardware of this systme is in detail described, the capability of this system is also demonstrated by showing the results of various kinds of tests described above. In addition, the performance can be evaluated in an attempt to measure elastic Young's modulus of clay at very small strains by examining the effects of drainage conditions, stress history and strain rate.

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In this paper, the applicability of the risk assessment methodology considering socioeconomic loss due to the collapse of discontinuous rock slopes was investigated. In detail, this study selected the slope consisting of the several unstable rock blocks as the example to investigate the occurrence of the various collapsed patterns of rock blocks, and evaluated the occurrence probability of the rock slope failure by adopting Monte Carlo simulation using DDA. The results showed that the proposed method has great possibility to make decision of the rational countermeasures in accordance with expected losses, which were described as monetary value.

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The sand compaction pile method is the most frequently used methods as a countermeasure against liquefaction of sandy deposits. The design of the method, which is the determination of the replacement ratio with sand piles, is conducted by using the SPT N-value and fines content of a soil layer and the targeted N-value. This paper describes the relationship between the replacement ratios and the increments of N-values in between sand piles based on the field data obtained in ports and an airport in Japan. And the effectiveness of a conventional method for the determination of the replacement ratio is discussed with the field data. It is found that the N-value before compaction affects the increment of the N-value, and that the influence is not considered in the conventional method. A new method to predict the increment of N-values by compaction is proposed on the basis of the cyclic shearing mechanism of soil in between sand piles during compaction. The new method is validated with the field data.

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Cement treated soils are often cast underwater in coastal constructions. If the soil separates seriously during the process of underwater casting, there is the possibility to result in environmental impacts on the surrounding water. Underwater casting methods of cement mixed soils are explained. Practical examples by compelled casting method are presented. This method is to cast cement mixed soil underwater by erecting the casting pipe into the freshly cast ground and to expand it silently. Turbidity and pH actually observed in projects are also reported.

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While determining the bulk density of a clay specimen, there are possibilities that the bulk densities of different specimens differ from each other depending on the method of specimen preparation. One of the reasons for this is degree of perfection during the preparation of specimen. In this paper, the authors try to examine the difference due to errors in measurement and then study the influence of the method of preparation. The major findings are: 1) Although the effective value of bulk density is up to three decimal points, the dimensional measurements are made with a vernier caliper of minimum reading up to only 0.005cm and 2) The shape and size of a specimen prepared by trimming method are more or less similar to those of a specimen prepared by tube method.

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