This paper describes the results of the experimental studies on strength-deformation characteristics of a sensitive clay subjected to repeated loading.
The repeated load was applied to the soil specimens consolidated in advance at various confining pressures, and excess pore pressure and deformation of the specimens were determined. Furthermore, strength of the specimens after application of a certain number of repeated loading and those after consolidation were compared.
Since bonding between soil perticles in the Osaka sensitive clay is broken dwon by repeated loading, strength recovery is rather small even after reconsolidation.

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In order to examine the occurrence of slope failure, we present some statistical results concerned with the factor of slope failures, which are occurred in sandy soil beds (Narita group), argilla- ceous rock beds (Kazusa group) and Kanto-loam beds. Site characterization was carried out using geological data analysis and quantification theory. In general, the results on the analysis show that (1) gradient of a slope, (2) rainfall and (3) existence of slope failures in the past are the main factors of slope failure. However their categories have some differences regionally, because of the conditional differences of slope surface and/or soil properties.

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Powder grouting method, by which surface improved cement particles are injected to the ground by means of compressed air, can ensure the injection length required for soft rocks. In this paper, a model of powder grouting mechanism is presented by considering the interaction between adhesion of a cement particle and drag force by air. A criterion for ensuring the satisfactory injection is also presented by the use of simplified analysis based on the model and a simulation analysis in which DEM is employed.

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Many types of plastic-board drains have been developed. For understanding the drainage performance of these drains, large-scale consolidation tests were carried out with plastic-board drains and sand drain. Factors influencing the drainage performance of these drains were investigated focussing on: flow characteristics of pore water; consolidation of clay in the close vicinity of the drain; deformed shape of drain; migration of fine particles; well resistance; formation of smear zone and its effect on consolidation.
A two-layer smear zone model is proposed for estimating the influence of smear zone on consolidation of clay in vertical drain system.

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This paper gives new analytical solutions to describe the two-dimensional elasto-plastic behavior of a rock opening under non-hydrostatic loading. The rock mass is assumed as a linear dilatant material and exhibits post-failure behavior after the peak stress. Based on the analysis of the loading history of in situ stress state, the plastic behavior and modes of plastic zone around the opening are explicated to evaluate the stability of the opening. Explicit formulation of the plastic stress field and of the plastic radii, which is applicable in every case for two-dimensional model, is obtained using a coupled Plasticity-Complex Function Method. The adequateness of the proposed method is verified by some case studies.

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This paper deals with the consolidation settlement prediction based on the observation of the earth fill which is constructed on soft clay layers. A new state space equation of settlement is proposed considering the influence of secondary compression. It shows that the unknown parameters of the model can be estimated by the adaptive observer which is proposed in this paper. This paper describes a new way to predict the future settlement with the observed data under construction. This method was applied to actual observations. It has been confirmed that this method is effective for predicting the settlements with inclusion of secondary compression.

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During shield work, the shield machine is driven foward by using the mechanical jacks behind the machine and the excavated soil in front of the cutting face is taken into the machine. In order to analize the ground behavior during shield work considering the execution procedures, it is necessary to simulate the advance of the shield machine and the excavation.
In this study, excavating elements arranged in front of the cutting face is newly proposed, which models the ground disturbed by cutting. The advance of the shield machine and the excavation is simulated by using excavating elements and rearrangement of finite element meshes. The stress-deformation behavior of soil during shield work was examined in detail, based on the comparison between the results of F. E. analyses considering the execution procedures and the field measurement results.

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It is not easy to know the in situ strength parameters c and ∅ of gravelly soils because of difficulty in getting the undisturbed samples for the laboratory test and also in performing the in situ shearing test. In order to overcome this troublesome problem, the authors tried to know c and ∅ of compacted gravelly soils by use of the passive pressure type field shear test using the 30cm×60cm bearing plate and compared the obtained values of c and ∅ with the results of in situ direct shearing test using the 30cm×30cm×18cm shear box. Based on these experimental works, it was made clear that the passive pressure type shear test is an easier and effective method to know the in situ strength parameters c and ∅ of soils.

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This paper described the difference of the estimation of geomechanical behavior between two-dimensional analysis and three-dimensional analysis from a viewpoint of effective stress. And this investigation made it clear that the application of methods considering progress of face for excavation analysis is inevitable in order to estimate reasonable stress path due to excavation based on the concept of effective stress.

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Unstable shearing deformation of granular materals is accompanied by characteristic deformation modes. As a tool to study these characteristic modes, an eigenvalue analysis based on the stiffness matrix of granular assemblies is presented. This eigenvalue analysis is performed for data obtained by Granular Element Method whose algorism utilizes stiffness matrix concept. Definition of characteristic quantities called the eigen mode coefficient and the norm of eigen mode expansion is also presented. Application of the method to a simulation of bi-axial shearing test shows the significance of the lower eigen modes. It is also shown from an artificial test with infinite friction that slippages between grains play important roles in characteristic deformation.

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The analytical proposal was investigated through a series of model tests on the bending behavior in the longitudinal direction of shield tunnels with secondary linings. The analytical model is composed of beams and springs which simulate the primary and secondary linings, joints and the interaction between the linings respectively. In the experimental study, firstly, concentrated load was applied to the test models to confirm effectiveness of the analytical model. Secondly, the interaction between tunnels and the ground was investigated through the tests in the model ground.

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A sea reclamation has been performed using dredged clay for the Haneda International Airport expansion project. Since the thick ground has an extremely high water content, fabri-packed sand drains, which are sand drains wrapped by envelopes of geotextile, are planned to be used. A series of centrifuge tests was performed changing the tensile rigidity of the geotextile to investigate the effect on the consolidation behavior of the ground. The study shows that the fabri-packed sand drain functions well as a drain even in the extremely soft soil. And also revealed is that the anticipated concentration of the fill pressure remains small if an appropriate geotextile is selected.

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The purpose of this paper is to reveal the fundamental characteristics of inherent anisotropic Toyoura sand under drained shear conditions. Towards this end, monotonic loading tests with fixed principal stress axes, and loading tests with rotation of principal stress axes were carried out using a large hollow cylindrical apparatus. Through the analysis of the experiment results, the characteristics regarding 1) the hardening law using the concept of a field of hardening moduli, 2) the principal deviatoric strain increment ratio, and 3) the dependence of the maximum principal strain increment direction on the stress increment direction, are clarified taking the effect of b-value into consideration.

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Measurements of rock deformation, lining stress and others were carried out at many sites during excavation of large scale caverns. Through the measurements the mechanism of rock behaviour has been cleared: a) deformation of rock consists of discontinuous displacement and continuous displacement, b) ratio of these two displacements differs by kinds of rock. A new idea of design on lining structure was proposed.

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A series of centrifuge model tests of heavy tamping was carried out to investigate the effect of tamping conditions, such as ram mass, drop height, ram base area and number of tamps, on ram penetration, ground compaction and ground deformation. The model is 3-D axi-symmetrical but semi-cylindrical sandy ground of 30cm in diameter and 20cm in height, the center of which the semi-cylindrical ram tamped in a 100g centrifugal acceleration field. The ground compaction and deformation are governed not by the tamping energy but chiefly by the ram momentum and square root of number of tamps.

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This paper describes the strength obtained from in-situ vane shear test. The undrained strength of vane shear test is formulated based on the elasto-plastic constitutive model proposed by Sekiguchi and Ohta (1977). The stress condition at the failure for the vane shear test used in the formulation are theoretically derived from vertically and horizontally direct-shearing models. Introduced are the effect of shearing rate and anisotropy of vane strength in K₀-consolidated clays through comparing the theoretical strength with measured values. And the last part of this paper is devoted to the discussion of the difference between the vane strength and the unconfined compression strength popular in Japan.

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This paper describes the behavior of ground anchorages installed in a single stratum under tensile load. It is also aimed at showing the results of pull-out tests applied on actual anchors installed in Kanto-loam stratum. In the end. this paper comes up with a predicting method of load-displacement curve and load distribution curve derived from the differential equations suggested by H. B. Seed and L. C. Reese.
Displacement and load distribution of anchors computed by the predicting method were compared with the results of pull-out tests. By changing rigidity of anchors, there was good agreement between the computed and the observed load-displacem ent curves. On the other hand, the lack of agreement between the computed and the observed load distribution curves under high load is presumed to be due to the variation in skin friction with depth.

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In order to control the frost damages by frost heaving or the translation of harniful object by pore water seepage, interception layer of capilaly flow is constructed in the ground. In this paper, laboratory freezing test used by fine graind sand were put into operation and details of water migration, heat flow and water pressure change were measured under closed systein conditions. The results of experiments were compared to the results of numerical analysiaes using integrated finite difference method with coupled heat and ground water movement. It is confirmed that the Simulation of ground water movement is probable in unsaturated conditions.

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The relation between the total kinematic energy and dislocation energy of soil in poie-water is derived from a physical premise and the conservation law of the multiphase-continuum, assuming that the internal friction of soil is idealized by the sliding block model. A pair of material constants are identified to characterize the strength of soil against liquefaction. The procedure to measure them from the cyclic undrained test data is developed. This method is applyed to the liquefaction observed in the Kawagishi-cho during the 1964 Niigata earthquake.

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Two different seismic borehole techniques are compared in this paper: One is a common downhole method with the source at the ground surface and the receiver in the downhole, and the other is a technique called suspension method in which both the source and the receiver are on the single sonde in a borehole. P-wave and S-wave velocities are compared between these test results using the same borehole. In addition, the downhole method is used to measure the damping with a reference seismometer near the surface. A cyclic torsional shear test and ultrasonic pulse test are also performed on undisturbed samples in order to compare the in-situ test results with those in laboratory. To this end, the writers summarize the comparisons of elastic wave velocities generated by in-situ measurements and laboratory tests. Direct application of these test results to the other fields will require further research.

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