Isotropic consolidation and drained triaxial compression shear tests were performed on the undisturbed sample of peat which contained a considerable amount of humic wooden chips and vegetal fibers. After the consolidation and shear tests, humic wooden chips and fibrous elements of peat sample were dried under vacuum freezing condition and then the measurements of pore size distributions were carried out by using the porosimetry apparatus of mercury intrusion type. Based on the test results, the changes in pore size distributions with isotropic consolidation and drained shear were investigated on both the fibrous element and humic wooden chip involved. It was found that the measurement of pore size distribution would be a help in the explanation of mechanism of change in peat structure with volume changes in consolidation and shear deformation processes.

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It is well known that borehole pressurization generaly produces a longitudinal fracture even in a borehole drilled not parallel to any far field principal stress direction. In such case, however, angular position of the fracture may be formed from crack initiation inclined to the borehoie axis, whose direction is perpendicular to the maximum tensile stress on the borehole boundary. Hence, the authors have developed a strict back calculation system for three dimensional stress, determination, using a method for unconstrained optimization, and they carried out back calculations in order to examine reliability of the conventional routine calcultion. They also applied it to reappraisal of the past stress measurement by double fracturing method, which was carried out with four other methods of stress measurement at the formation in abnormal stress state. It is suggested from the examinations that strict calculation should be introduced only when the fracture impression shows that inclination of fracture initiation is significantly large.

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In homogeneous soil slopes, underground water flows down, forming a definite free water table. However, due to the many kinds of permeable layers in natural slopes, groundwater must flow through either the permeable layers or cracks in the ground. According to the results of piezometric measurements of waterheads in natural slopes, the waterheads are high in shallow places and low in deep places. This means that porewater pressures are nearly zero in all depths of stable slopes. During rainfalls, waterheads gradually rise in the permeable layers and a flownet of deep streams is formed such as those in slopes of homogeneous soil.
Behavior of groundwater during rainfalls can be explained through numerical simulation analyses using a computer.

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This paper deals with a method of estimating the railway embankment collapse in times of heavy rainfall by means of a multivariate analysis. The critical rainfall is assumed as a continuous rainfall multiplied by the maximum hourly rainfall. Then the critical rainfall is given by variables of the embankment such as soil and structural properties, the surface ground geotechnical characteristics, the water collection and seepage, and the experienced rainfall. By use of the proposed method, we can approximately predict the critical value of rainfall to embankment collapse.

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In this investigation, compaction tests were firstly preformed on the soils of clay, river sand, loam and mixed samples. The mixed soils were reconstituted from the samples of clay-river sand, loam-river sand and clay-loam in various ratios of mass. After the compaction, all the compacted soils were dried in vacuum freezing condition in order to prevent the drying shrinkage, and then the measurements of pore size distributions were carried out by using the porosimetry apparatus of mercury intrusion type. Based on the results of compaction test and the measured results of pore size distribution, the pore structures of compacted soils were discussed. Moreover, permeability tests were also performed on the compacted loam samples and the consideration was made on the relationships between pore structure and permeability. It was found that the pore structures of compacted soils were influenced considerably by the values of water content and the clear difference was recognized between dry side, optimum state and wet side, respectively. It was also pointed out that the changes in permeability with water content were appoximately corresponding to those in pore structure.

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A series of K₀-consolidation test on saturated remolded clay with triaxal testing apparatus was perfomed to investigate the influence of the difference of testing condition on K₀-value.
A new automatic K₀-consolidation system was devised which can establish the K₀ condition by increasing vertical stress up to the desired value while controlling lateral stress to prevent the occurrence of lateral strain of the specimen within the limit of ±0.01%.
Based on the test results, suitable methods of horizontal strain control, rate of vertical stress loading, drainage condition etc. were proposed.

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Composite ground which is improved by sand piles such as the sand compaction pile method is deformed three-dimensionally under any loading condition, approximated analysis by two-dimensional methods are performed usually. In this paper, composite grounds are analyzed by the two-dimensional FEM and the quasi-three-dimensional FEM with the special element called ‘Multi-link element’ which takes account of three-dimensional deformation between soils and piles. As a result, the two-dimensional FEM cannot express strength of composite ground well. Then various composite grounds under undrained conditon are calculated with ‘Multi-link element’. Consequently, interesting characteristics for failure pattern and stress share are obtained.

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The bearing capacity of soft clay ground improved by sand compaction piles is investigated based on the limiting equilibrium analysis making distinction between undrained and drained conditions for sand. Prior to the analyses, a series of triaxial compression tests of clay with a sand pile is carried out in laboratory. The test results show that the undrained condition for a sand pile with negative excess pore pressure is durable for a long time. The bearing capacity is solved with a variety in a sand-replacement ratio from 30% to 70%, which provides the information required in design practice both on the stress concentration and on the necessary length of vertical sand piles. On the basis of this analysis procedure, a field loading test of composite ground to failure with a low sand-replacement ratio that was made by the Ministry of Transport of Japan in 1987-1988 is also analyzed and discussed.

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There is a recent general interest in tunnels which were underwent large deformations. The international Society for Rock Mechanics (ISRM) has established a working group for this purpose. This particular study is concerned with the squeezing phenomenon with some particular references to the swelling phenomenon. The present study mainly attempts to clarify the squeezing phenomenon of ground about tunnels and its mechanism and associated factors by studying carefully observed failures on site and laboratory model tests. Then, a new method is proposed to predict the possibility of squeezing of ground in tunnelling projects.

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In this paper the authors propose a quantiative method for determining optimal tunnel support structures by analyzing the results of displacement measurements performed during construction. In the proposed method, the “normalized initial stress” is considered as a design parameter; and it is assumed to be a function of the support structures. Thus, the sensitivity coefficient can be defined, and easily calculated by differentiating the normalized initial stress with respect to the quantities of the support structures, such as: the number and length of rock bolts, thickness of shotcretes, etc. In order to determine the quantities of optimal support structures, an optimization problem is formulated: the quantities of support structures are controlled for maintaining the maximum shear strain occurring in the rocks around a tunnel within its allowable value. In the formulation of this optimization problem, the sensitivity coefficient becomes extremely useful. A case study is shown in order to demonstrate the applicability of the proposed method for engineering practices.

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To investigate the effect of underground water on the mechanical behavior of shallow sandy ground tunnel, laboratory model tests were carried out by using a pressure controllable tunneling device and the model ground by piling up aluminum rods with various groundwater level. Descrived was the numerical procedure to back-analyze the non-linear constitutive parameters and coefficient of permiability from the monitored displacement during tunnel excavation. It was verified with hypothetical case studies and the model tests, that the proporsed procedure can be successfully estimate the constitutive parameters from the monitored movements at construction sites.

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In this paper a new numerical method to analize a three-dimensional seepage in saturated/unsaturated porous media is proposed. This method bases on SSOR-PCG method. This method consists of slice successive overrelaxation (SSOR) and preconditioned conjugate gradient (PCG) method; the former is used for transformation from a three-dimensional finite element mesh to two-dimensional mesh slices and the later is able to solve the matrix-equation for each slices efficiently. The validity and performances are verified through the five kinds of three-dimensional seepage problems. Appling this model to simulate three-dimensional seepage flow problems, computer storage is explosively reduced compared with conventional numerical models and more reasonable analysis is realized.

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This paper proposes the design method in the longitudinal direction for the shield tunnel at a sharply curved section.Firstly, member forces are calculated using the beam-spring model. Stresses and deformations at ring joints are, then, calculatated in order to design segments. Secondary, the propriety of the method is shown comparing with data obtained by in situ measurement. Finally, typical examples for designing segments at a sharply curved section are presented.

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Soils may be regarded as a mixture, because soil consists of various sizes of grain particles. A method for predicting the stress-strain relationship of the mixtures is proposed. A new definition for stress and strain is used to express the average values of stress and strain distributed in the mixtures. The stress-strain relationship of the mixtures is derived from considering the stress distribution and the strain energy of the mixtures. The effectiveness of the proposed method is verified for the mixtures with two different elastic materials. This idea is applied to sand-clay mixed soils by evaluating the soil structures.

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In order to invesitgate the strength and deformation characteristics of the reclamation material (Kada-gravel) of Kansai-International-Airport, a series of large scale triaxial compression test was performed with the specimen (h/d=2400mm/1200mm) which has the field glading and field density. It was found the following from test results. This material has the maximum particle size of 300mm and the uniformity coefficient of 26.2. The gravel show a failure envelope with pronounced curvature at low stress level, i. e. the value of strength parameter is strongly dependent on the value of σ₃.

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A series of large scale loading tests in a pneumatic caisson was conducted at a construction site of bridge foundation. Experience of the project was described from planning stage to the execution of the tests. Advantages and difficulties of loading tests in caisson were discussed and ways how to overcome these difficulties were described. Detailed observations of soil conditions and of failure mechanisms were also described. Interesting pictures of failure mechanism were obtained showing clear shear bands developing underneath the footings.

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