The method to quantitatively understand discontinuities in the rock mass is studied based on the stereological theory. Modelling these discontinuities, distributing with orientation and frequency in the rock mass, is primarily important in estimating the mechanical behavior of the discontinuous rock mass. In this paper, proposed method is applied to the in-situ geological survey at the underground cavern for the Akaishi hydroelectric power plant. The 3-dimensional distribution of discontinuities is modeled using the geological survey data. The results demonstrates that the density of distribution and orientation of discontinuities in the rock mass are successfully modeled by the method.

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The investigation of liquefaction-induced ground failures during the Kanto earthquake in Tokyo lowland shows that the sandy deposits containing only a small amount of fines were more prone to liquefy rather than those containing considerable amount of fines. The undrained cyclic strength of undisturbed specimens containing fines is considerably strong in spite of small SPT N-values. The formula estimating liquefaction strength proposed herein is formed not only with SPT N-values, effective overburden pressure and mean diameter, but also with fines contents and confining stress. The grounds which consist of liquefiable sandy deposits within surface layers are generally likely to induce severe ground failures. So a criterion of liquefaction susceptibility with F_L values of surface layers is proposed herein in order to estimate liquefaction potential for wide area. According to the comparison between the liquefaction analysis for boring records in actually liquefied sites and unliquefied sites during the earthquake, combination of F_L values on sandy surface layers and P_L values gives more reasonable estimation.

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The total rainfall till the slope failure was investigated by numerical analysis considering the physical properties of soil. The regions which were made the object of this investigation are Kure in Hiroshima pref., Tochuyo in Ehime pref. and Kagoshima pref.. The soil of Kure and Tochuyo is made of decomposed granite soil and Kagoshima is made of shirasu. The representative physical properties of soils of failed slope was examined. The successive total rainfall causing to slope failure was obtained numerically considering the various characteristics of slope. The critical rainfall causing to slope failure increases in the order of Kure, Tochuyo, Kagoshima. The results of numerical analysis agree quantitatively with the data of slope failure.

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In this investigation, clastic samples of mudstone produced by in-situ slaking and crushed samples obtained from sound blocks of mudstones which were not affected by the effect of slaking were used, and the compaction properties of crushed mudstones were investigated. The compaction tests were carried out under various conditions. After compaction tests, grain size analyses were performed and the states of grain crushing during compaction were investigated. In order to estimate the compaction effect, compression and CBR tests were also performed on compacted samples. It was reported that the compaction properties of crushed mudstones were influenced considerably by compaction condition, effect of submergence and initial gradation of sample. In particular, as the submerged samples show remarkable grain crushing during compaction, they have large value of dry density.

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This paper deals with some problems encountered in the back analysis of measured displacements carried out during the excavation of tunnels in order to monitor their stability.
The paper consists of two parts. The first part deals with the problems that arise when the displacements have already taken place before the measuring devices are installed and the first reading is taken. Hence, the results of the back analyses become questionable. To overcome this dilemma, three-dimensional back analysis is recommended.
The second part is for a discussion on the accuracy of the back analyses, that generally depends on the way in which the input data is introduced in the analyses. In this paper, the “dual back analysis” method is proposed to increase this accuracy.

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In order to identify liquefaction susceptibility for wide area, it is necessary to have as much information as possible in the area under consideration. In this study, a computer aided system has been developed to facilitate engineering decision-making concerning liquefaction susceptibility. The man-machine interactive system and graphic display capability give an engineer not only the final evaluated result but also information needed to understand the background knowledge on the factors of liquefaction likelihood. The liquefaction potential lots map in Tokyo Lowland was compiled from the indices of liquefaction potential analysis, the information about liquefaction generated during the Kanto earthquake, and the characteristics of geography and geology.
The system engineering procedure was useful for the interactive evaluation of a great amount of information and for the decision about poorly defined problems such as the assessment of liquefaction potential mapping. A result of these studies showed that the liquefiable area was about one forth of Tokyo Lowland.

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The hydraulic fracturing technique as a potential method for determination of in-situ stresses has the advantage in contrast to the stress relief techniques in that it is not in need of the elastic modulus of rock. However, the level of confidence in the measured maximum principal stress is lower than in the minimum principal stress. In many instances, the maximum principal stress, generally the more important, is not directly measured.
In order to seek the possibility to measure the maximum principal stress directly from the shut-in pressure data by making a (pair of) artificial longitudinal slot (s) along the minimum principal stress direction, the authors carried out numerical analyses by boundary element method and laboratory tests using cubic specimens of mortar, which has a borehole with slot. This paper describes the results obtained from these experimental and numerical works.

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A convenient method of test for permeability of unsaturated soil under controlled air pressure was examined. It was reflected on the improvement of procedure to measure a little rate of discharge infiltrated, headloss of filters attached to soil sample and so on. As a result, a guide to select filter in consideration of permeability of soil was obtained, and water content distributed through soil column was verified to be approximately uniform. It was also found that a fairly great value of hydraulic gradient was allowable to be burdened to sample, and that degree of saturation could be controlled corresponding to the air pressure, which made operation time shorter than in the previous procedure.

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A non-linear analysis for a circular soft rock tunnel in a hydrostatic stress field has been performed theoretically, in order to make squeezing characteristics clear. The material behaviour is described by a non-linear elasto-plastic stress-strain model and a non-linear failure criterion proposed by Brown. The ratio of strength and initial tangent modulus of a stress-strain curve is thought to be independent of confining pressure. Closed form solutions of stresses, strains and displacements have been obtained. By performing parametric studies, effects of the non-linearity of stress-strain relationships on a stress pass, squeezing characteristics and relationships between internal pressure and displacement have been made clear.

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This study was conducted with the aim of applying three dimensional Boundary Element Method in analysis of ground excavation. The methods studied were dead load analysis for evaluating initial ground pressure and stage excavation analysis which permits consideration of construction schedule. And a tunnel intersection problem and a shaft excavation problem were analysed using these methods.
Following results were obtained.
(1) By supplying dead load analysis method, it is possible to obtain three dimensional initial ground pressure accurately.
(2) Accurate analysis of three dimensional stage excavation is possible with Boundary Element Method.
(3) These methods can be applied to practical problems for three dimensional underground excavation.

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The block theory to analyze three dimensional stability problems of discontinuous rock masses is applied to the actual discontinuous rock slope. Taking into consideration that the geometrical information about discontinuities generally increases according to progressive steps of rock investigation in field, the method adopted for analysis is divided into following two steps; 1) the statistical/probabilitical analysis using information from the primary investigation stage which mainly consists of that of natural rock outcrops, and 2) the deterministic analysis correspond to the secondary stage using exploration adits.

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An electric heater was inserted into a hole bored in the center of a 300mm cubic granite block, and the temperature of the heater was increased to 500°C at the rate of 200°C/h. An visible crack was produced from a lateral surface to the center hole through the block at 107 minutes after the start of heating. The distribution of temperature measured with thermocouples located at various points in the block indicated that this cracking was caused by the thermal tensile stress in the circumferential direction. Acoustic emission activity and P wave velocity were monitored during this experiment. These monitoring results corresponded to the cracking in the specimen, therefore it was assured that these monitoring methods are useful for thermal cracking of granite.

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The experiments on the mechanism of damage of relatively small sized concrete U-trough with ground freezing were made. For this purpose, 450 millimeter concrete U-troughs specified in JISA-5305 were experimentally set, and the collapsing force, deformation, and so on arise at the troughs in winter season were measured. Through this study, the following results were obtained. 1) The collapse of concrete U-trough occured after ground freezing mainly had origin in frost heaving. 2) Under a certain condition, the magnitude of frost heaving pressure acting on the trough was far over the destruction resistance of tested trough. 3) The effect of some countermeasures attempted in this study were evidently recognised.

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Two-way strain controlled cyclic simple shear tests with different loading periods (0.2-10s) are performed for normally and overconsolidated kaolinite clay specimens (OCR=1, 6). The specimens are subjected to cyclic shear under undrained condition and subsequently the cumulated excess pore water pressure are dissipated. In conclusion, it is clarified that for normally consolidated clay, the larger the period of cyclic shear, the larger the excess pore water pressure becomes and that with the increase of OCR, effects of the period on the cumulated excess pore water pressure disappear. As for the settlement, however, the effects of period can not be seen.

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In this paper, an attempt is made to apply the fuzzy sets theory to the rock mass classification of granite tunnels. By using the fuzzy regression analysis, it is possible to develop an objective and simplified equation to classify rock masses, which can be applied to a tunnel face under construction. Each classified region derived from the proposed equation has sectional and continuous values with possibility distribution. Discussions on the adequacy of the equation in rock engineering, the comparison with the usual statistical approach and a methodology of modification to adapt it to each granite tunnel are mentioned.

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The objective of the present paper is to study estimations of the permeability on discontinuous rock mass.
Firstly, two-dimensional numerical analyses on seepage flow through geological discontinuities (called joints) are carried out to examine the theory proposed by Oda. Especially, the effect of the aperture distribution of joints on the permeability tensor is examined in detail. Secondly, the field method, known as the Lugeon test, is investigated on the scale effect of the packed-off interval (stage length). This effect on the estimation is discussed with the results from the numerical analyses.
Finally, the effects of the aperture distribution of joints and the packed-off interval on estimations of the permeability are demonstrated.

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It is well known that local earth pressure acts on pre-existing shield tunnel for example where parallel shield tunnels are very close to each other especially in poor cohesive soil ground. Accordingly, field measurements and in-situ measurements were performed to investigate the mechanism of ground behavior around pre-existing shield tunnel and its lining in case of later shield tunnelling. This paper aims to make clear the relationship between local earth pressure due to later shield tunnelling and cross-sectional forces especially bending moment of pre-existing shield segment rings, and to verify the authors' proposed pseudo-three dimensional numerical analysis method of segment rings based on the beam theory and the cylindrical shell theory in the longitudinal direction. As the result, we could propose the value distribution of local earth pressure during later tunnelling in use of the earth pressure type shield, and confirm to coincide almost with the measured bending moment and caluculated ones of the authors' method.

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This paper proposes Weibull distribution to describe the stress-strain relationship in the softening process of rocks under uniaxial compression. This distribution of damage of rock is given by the compliance of the specimen. Experimental results using marble specimens showed that the Weibull distribution was suitable to express its internal damage. Moreover, it was shown that the softening process generally was aproximated to the composite Weibull distribution, and this distribution was separated by Monte Carlo simulation. The first separated distribution (F₁) may mean the probabilistic character of microcrack propagation and the second one (F₂), the initiation respectively.

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This paper discusses the mechanical behavior of ground bottom heave due to excavation. First, the heave fluctuation actually measured at 3 large-scale excavations are discussed. Then, the heave mechanism in examined by comparing the measured values with theoretical values obtained from coupled stress-flow finite element analysis. Furthermore, elastic moduli under load removal conditions (E_r), for layers composed of sand and clay, are estimated by back analysis. The local iterated extended Kalman filter of control theory combined with finite element method is applied to the back analysis in order to consider probabilistic features of measured values.

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When designing an earthquake-proof of shield tunnels, it is necessary to take into due consideration the axial force which arises from phase differences in seismic wave transmission in the axial direction. The important point of the analysis is whether the evaluation of the axial tensile stiffness of the tunnel is valid.
In order to investigate the axial stiffness of shield tunnels, tensile loading tests were conducted using a specimen of actual size with primary and secondary linings, which corresponds to a shield tunnel of about 14m O. D..
The results clarified the relationship for the entire lining strain-stiffness, and information was obtained concerning the behavior of lining components, such as cracks in the secondary lining and bond failure of reinforcing bars. Further more, in order to characterize the behavior of long undersea tunnels during earthquakes, seismic response was calculated from the strain-stiffness relationship of the lining obtained by these tests.

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This paper investigates the relation between solidified shape and gel time of grout in the stratified deposits. Through the injection tests with the large injection apparatus, the main conclusions are summarized as follows; 1) In the stratified sandy deposits, the long gel time grout tends to permeate into the layer of which permeability is the largest. On the other hand, the short gel time grout generally permeates uniformly. 2) If the soft clay layer is contained in the stratified deposit, the injected grout tends to penetrate into the border between the clay and the sand or into the clay. Especially, in the case of short gel time grout, the most part of injected grout penetrates into the border or the clay, even if the injection point is in a sand layer. Therefore the permeated grout in sand layer is very little.

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This paper deals with settlement of the abutment backfill due to earthquakes. A few such case histories are described. The region which comes under seismic influence is indicated by distance from epicenter and magnitude of earthquake. Some multivariate analyses is performed, and discriminant equations which distinguish between settlement more or less than 10cm are proposed using seven variables: width of embankment, SPT N-values of embankment, height of embankment, SPT N-values of ground surface, depth of subsurface layer, height of abutment and acceleration of ground surface. Then multiple regression equations are proposed particularly for the settlement more than 10cm. This enables us to estimate quantitatively the settlement of an abutment backfill during an earthquake.

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This paper attempts to propose the formulas for estimating vertical spring constants of the pile top under a condition named the elastic limit state as well as to grasp quantitatively this limit state against the vertical force of a single pile.
On the basis of a new definition of the ultimate bearing capacity through the settlement level (settlement of the pile top/diameter of pile), we present an equation for predicting the ultimate bearing capacity which is applicable irrespectively of the supporting system of piles.
Then, evaluation of safety factors for the ultimate limit state is made by considering accuracy in this equation.

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The paper presents the results of centrifuge model tests and upper bound calculations on two-dimensional unlined tunnels in two different normally consolidated cohesive soils with the plasticity index of 10 and 25. The upper bound calculations were carried out by taking the variation of soil strength with depth and the strength anisotropy into account. It is found that the undrained stability of the tunnels increases with increasing tunnel cover-to-diameter ratio and that observed surface settlement profiles are different for the two soils. The critical tunnel pressures as well as the collapse mechanisms deduced from the bound calculation compare well with the observations. It is confirmed that the surface settlement profiles can be represented by the error functions fairly accurately.

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It has been very difficult to evaluate with accuracy the behavior of rock mass around tunnel, because rock mass possesses time dependent properties. The time dependent displacement of tunnel consists of two mechanisms that are elastic one due to the progression of tunnel face and another due to the visco-plastic properties of rock mass. In this paper, it is emphasized that these mechanisms may be separated by theoretical approach. The tunnel considered is circular in shape, and is assumed to excavated in constant velocity in the isotropic linear visco-elastic homogeneous media. In addition to these assumptions the idea of equivalent initial stress is introduced. It means that the initial stress varies with time correspond to the velocity of progression of tunnel face. The exact solution of convergence is clearly obtained under these conditions using correspondence theory.

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In our previous paper the cyclic shear tests on sand are performed using Kjellman's type simple shear box, fixed on a shaking table. The tests are performed under a vertical stress (σ′_z) of 49.4kPa. From the test results, the equation calculating the principal stresses induced in sand is obtained. Furthermore it is found that the internal friction angle of sand decreases 2.5° with increasing a seismic coefficient k_h by 0.1. In this paper to confirm this result the same tests as previous ones are carried out under σ′_z=29.8kPa. As a result it was found that the result of this investigation is the same as that for the previous one. Therefore this test results are presented in a generalized form.

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