It is natural that rock mass has many discontinuities. Detection of discontinuities is one of the most important factors for site characterization. Mapping of discontinuity networks along a scanline or on a defined area is an established technique for sampling the attitude and spacings of the discontinuities. However, the method to evaluate and simulate rock discontinuities is not established yet. This paper describes two- and three-dimensional modeling methods for discontinuous rock masses based on the quantitative estimation of the discontinuity distribution. Several techniques to interpret discontinuity mapping data have been proposed and evaluated.

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In order to make clear squeezing characteristics of a tunnel in soft rocks and to determine reasonable tunnel construction sequences, a theoretical analysis and tunnel model tests have been performed. In the analysis, the following factors are taken into account; (1) a non-linear stress-strain relationship which changes with confining pressure, (2) a non-linear yield criterion, (3) the ratio of strength and initial tangent modulus of a stress-strain curve is independent of confining pressure. Closed form solutions of stresses, strains and displacement have been obtained. Theoretical results obtained both by the non-linear analysis proposed and by the Kastner's elastoplastic analysis are compared with model test results. From the results of the comparison, appropriateness of the non-linear tunnel analysis is shown.

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This paper investigates procedures to determine soil parameters used in elasto-viscoplastic analysis based on the standard laboratory tests.
Some parameters of elasto-viscoplastic constitutive model are found to be related to unconfined compressive strength and oedometer test results.
Using the parameters obtained by interpreting these test results, finite element computations are carried out analysing trial embankments on soft ground. Applicability of the procedure to engineering practice is verified by comparing the computed results with measured field performance of soft foundations.

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In the chemical grouting for the improvement of the cohesive soils, the hydrofracture occurs in all cases. The object of this study is to investigate the mechanism of strength increase of cohesive soils by grouting. The increase of strength by grouting depends upon the formation of solidified grout, the consolidation by the injection pressure and moreover the cementing action between the cohesive soil and the liquid dehydrated from the solidified grout. These factors are influenced by the grout itself and the ground condition, such as the strength of cohesive soils before grouting, the exchangeable cation, and the buffer capacity of soil.

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In nature, discontinuities in rock mass usually exist in the form of joint sets. In the paper, an analysis method for the effects of such discontinuities on the dynamic responses of rock mass is presented by imploying the conceptions of damage mechanics theory. A numerical scheme by finite element method has developed and used to treat the problem of elastic wave travelling in jointed rock mass. In addition, an elastic wave experimental program has been carried on the specimen of mortal with artificial made joints. It has showen that the dynamic responses computed by the numerical approach using the method presented are in good agreements with those obtained in the experiment, and the applicability of damage mechanics theory to the dynamic problems of rock mass has been confirmed.

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In this study, the variation of mechanical characteristics for soft rocks in the salt concentration of solution contained in soft rocks changing have been examined and investigated. In this paper, the variation of longitudinal wave velocity for soft rocks is investigated by the surface phenomena of clay minerals in soft rocks.
From the results, it became clear that the longitudinal wave velocity for soft rocks decreased in the salt consentration becoming lower, but the longitudinal wave velocity for heated samples of soft rocks showed almost the same value.

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In an improved ground using a sand drain system, the difference in the rigidity between clay and sand causes the stress concentration on the sand columns in consequence of the progress of consolidation, thereby expanding the diameters of sand columns. In this paper, a consolidation theory is developed considering the rigidity of sand columns, on the assumptions that clay skeleton is anisotropic linear elastic, and sand columns are isotropic elastic body. And, the effects of the rigidity of sand columns and the anisotropy of clay acting upon the consolidation behavior are considered.
Besides, considerations are also given to the conditions of deformation in which the consolidation of the ground installed the sand columns is approximated by the use of the consolidation theory for the anisotropic hollow cylinder. The results thereof have arrived at the conclusion that the consolidation can be approximated by the use of the anisotropic hollow cylinder with the loading on the top surface, by restraining the displacement of the internal and external circumferential surfaces.

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The paper describes a new method to predict a quantity of leakage through a fill dam and subsoils. The main point of this method is to construct a network model for geological structure within a flow region. It is made of some nodal points and branches. The nodal point, which shows a soil deposit, is an imaginary spatial coordinate. The branch, on the other hand, shows a groundwater flow conduit. It has substantial parameters to prescribe the groundwater flow in the model, such as permeability, thickness and length of soil layer. These values can be given from boring and in-situ test results. In this study, however, they are found to be widely scattered even in the same branch. The Monte Carlo simulation helps us calculate the quantity of leakage considering those scattered values.

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In order to simulate the ground motion under arbitrary loading including rotation of the principal stress axes, the authors incorporate a proper constitutive equation in dynamic analyses. In the present paper, a parameter is proposed to consider the effect of stress reversal subjected to earthquake loading. The parameter is substituted in the Matsuoka's constitutive model (1986) that can evaluate the yield due to rotation of the principal stress axes. Simulations of simple shear tests, shaking table tests and liquefaction analysis of irregular grounds are carried out. Those numerical studies indicate that Matsuoka's model can be applied to the seismic response analysis of the ground under the arbitrary loading.

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In order to analyze the clay layer improved by sand piles, called the ‘composite ground’, a numerical method is proposed using the special plane strain element whose degree of freedom is reduced to two for each nodal point by constraint conditions. The three-dimensional behavior of the composite ground under plane strain condition can be analyzed by the two-dimensional FEM code using the proposed element. This element is also extended to analyze the coupled problem of flow in the ground such as ‘vertical drain’, which takes the stiffness of the drain into account. The proposed finite element method for the composite ground is checked by comparing the computed values with the three-dimensional analytical results as elastic and elasto-plastic materials.

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It is important in engineering practice that reliability analysis of embankment must be done considering uncertainties as well as randomness in load and resistance. The present study deals with reliability of embankment when a major earthquake occurs. First, the authors present a seismic reliability analysis of embankment in consideration of randomness and uncertainties of load and resistance using point estimate method. The objective of this paper is to develop the reliability analysis in order to evaluate the failure of embankment due to pore water pressure build-up. Secondly, the influence of randomness and uncertainties in the seismic load and resistance of embankment itself on the damage assessment is also discussed. Finally, the method is applied to the embankment damaged in the past earthquake.

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Recently, chemical soil stabilizations are actively adopted for the improvement of the soft ground on which roads or buildings will be constructed. In addition to traditional stabilizers of Poltland cement and lime, the industrial by-products such as fly ash and pulverized blastfurnace slag are also used for the purpose of increasing the effectiveness of cement and lime as a stabilizer and their effective utilization in soil stabilization. The objective of this study is to reveal the mechanisms of strength development of the compacted stabilized soils from a microstructural view-point. The compressive strength, modulus of deformation and pulse velocity of various compacted soils stabilized with cement, lime and lime-fly ash (or pulverized blastfurnace slag) were measured. Their microstructures were also characterized by the SEM observation and pore size distributions obtained by the mercury intrusion porosimeter. The relationships between strength and changes in microstructure in compacted stabilized soils are discussed.

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In order to investigate the particle crushing and shear characteristics of decomposed granite soil, consolidation tests and direct shear tests were carried out under unsoaked and soaked conditions. A new type of direct shear box with reduced friction was used to know the shear characteristics under low and moderate pressures. Using the strength parameter obtained from direct shear tests under both pressures, we calculated the safety factors of slopes. The results were summarized as follows: 1) Particle crushing of the soil due to the compression and the shear is considerable. 2) The failure line consists of two straight lines changing the slope at normal stress of σ=20kN/m² which correspond to the lower boundary of particle crushing region. 3) The degree of decrease in shear strength due to soaking is greater in the region of low pressures than at moderate pressures. 4) For shallow sliding failures, the safety factors under the low pressures is a little less than that under the moderate pressures.

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The purpose of the present paper is to depict the clay behaviour of long-term drained cyclic loading. The empirical relations of time-dependent shear deformation and cyclically induced pore pressure were formulated through the undrained cyclic triaxial test on plastic marine clay which is assumed to be close to an element test. An analytical model was presented by combination of the equation of induced pore pressure with the Terzaghi's type of consolidation theory. The model successfully explained the behaviour of generation and dissipation of pore pressure and volumetric change in clay during cyclic loading. It was suggested from the result of finite element analysis that the proposed model should be a clue to predict the deformation, settlement and stability of soft clay under long-term cyclic loading with inclusion of drainage.

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In order to evaluate the stability of river levee, the application of a logit model was attempted. On the basis of actual levee breaches, the probability of collapse for river levee was evaluated with the damage potential function consisting of characteristic factors of river levees. Eleven factors were selected of many possible factors of levee, and four logit models were formulated with them. As a result, the significant characteristic factors which affected the stability evaluation were specified. And it was found that probability of collapse “P” could accurately be represented as index for the stability of river levee. This paper also shows that the predictability of these models are sufficiently effective to evaluate river levee stability in the sense of its simplicity.

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This paper deals with the optimum method of a heat insulator for an adiabatic icicle prevention at tunnel-lining surface. The atmospheric conditions, which consist of yearly mean temperature, yearly amplitude and daily amplitude, are estimated as statistical values following an extreme distribution analysis. They are incorporated into a nonsteady state heat convection/conduction analysis about a tunnel-ground model with adiabatic treatment. Thus the material and the thickness of a heat insulator for the icicle prevention can be designed reasonably and economically on the basis of the periodicity of atmospheric conditions and the thermal conditions of a tunnel-ground.

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Granite specimens were cored at π/12 radian intervals within the grain plane, and then loaded at constant strain rates of 10^-5, 10^-6 and 10^-7/s. The compressive strength varied about 10% in the different directions and about 15% under different strain rates. Young's modulus at low stress levels differed about 40% in the different directions. The Young's modulus defined by the linear part of stress-strain curve hardly changed. When the loading axis inclined at small angle to the grain plane, the strike of the fault was parallel to the grain plane. Except in the above case, the strike was always parallel to the rift plane. A ratio of the dilatant strain to the number of acoustic emissions increased with decreasing strain rate. Four independent velocities showed that the crack closure continued to the last stage of the loading and also showed that the dilatancy anisotropy should be affected by the rock fabric.

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The stability of rock slopes during earthquakes are of great concern in rock engineering works such as highway, dam, and nuclear power station constructions. As rock mass in nature is usually discontinuous, the stability of rock slopes will be governed by the spatial distribution of discontinuities in relation with the geometry of slope and their mechanical properties rather than the rock element. The authors have carried out some model tests on discontinuous rock slopes using three different model tests techniques in order to investigate the dynamic behaviour and failure modes of the slopes in discontinuous rock mass. This paper describes the findings and observations made on model rock slopes with various discontinuity patterns and slope geometry. In addition some stability criterions are developed and the calculated results are compared with those of experiments.

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There have been nothing or few studies on the effect of disturbing frozen soils. An experimental study was carried out by using artificial undisturbed clay samples and was investigated by regression analysis. The obtained main conclusions are as follows. (1) The compressive strength and deformation modulus of frozen clay increased slightly by disturbing. (2) The reason why the strength and deformation modulus increase by disturbing seems to depend on decreasing of water content and increasing of dry specific gravity by disturbing. (3) If high sensitivity clay is frozen, its sensitivity ratio becomes nearly 1 and is not sensitive. (4) The more lime adds to clay, the less strength of unfrozen clay becomes, However, these effect almost disappear, if such a clay is frozen.

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Calculation method of stress in well structures built up with steel pipe piles is treated by means of Finite Fourier Integration Transforms.
The well structure of this kind is supposed to be structure of space beam which are connected to each other by axial joint springs.
Discussion is especially focused to an elliptic well having partition walls inside space. Three types of well: circle, square and ellips with two partition walls, are numerically taken up, and the results of the third type are compared with experimental values.

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The purpose of this study is to propose a procedure to predict groundwater behavior under new boundary conditions based on previous observations and on prior geotechnical and geological information. Also, special emphasis is given to the quantification of the uncertainties that are present in every stage of the procedure. First, the model parameters are estimated with involved estimation errors based on observations and the prior information by following an inverse analysis procedure. Second, the information obtained is used as input to predict the future behavior of the groundwater by introducing a stochastic finite element procedure. The final outcome of this procedure is the prediction of ground water under new boundary conditions with quantified uncertainties involved in it. A rather simple numerical example is attached to illustrate the results.

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Recently a stochastic finite element method (SFEM), which can treat stress analyses with stochastic variability, has been drawing attention particularly in the field of geotechnical engineering. This is due to the fact that design parameters such as material constants, external loads, etc., must be regarded as random variables.
In an ordinary SFEM, the probability density functions are usually assumed to be a normal distribution. The distribution of uncertainty, however, does not always follow the normal distributions in geotechnical engineering problems. Therefore, difficulties may arise when applying SFEM to non-normal distribution problems.
In this paper, a new method is proposed in order to overcome the above-mentioned difficulty of calculating failure probability. In the proposed method, the failure criterion is linealized at the failure point, and failure probability can be calculated on the integration of the linealized failure criterion by using random numbers.
Some numerical examples are demonstrated to verify the proposed method.

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Several kinds of diametral compression tests were performed to check what the major parameters that scatter tensile strength are. One of them was as carefully an arranged experiment as we could possibly do. Another one was a roughly arranged experiment, which is probably usually performed. Between these two extremes, three kinds of experiments varying in some parameters, like testing machine, cylindrical surface grinding, spherical seats and orientation of splitting plane, were carried out. Oshima granite was chosen for these tests. The tensile strength for the carefully arranged experiment showed minute scattering. Experimental results indicate that in order to get meaningful data, it is necessary to fix the split plane with respect to the axes of anisotropy, at least for granitic rocks and that the design of the spherical seats and the readjustment of the spherical seats after a slight loading are also important.

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Walls of piles have often been used as a stabilizing device for landslides. In this study, a series of laboratory model tests have been carried out to help elucidate the preventive mechanism of these piles. Namely, a pile or group piles were installed in a sandy model ground made by piling aluminum rods up on a bottom plate. The load acting on each pile and the ground movement around the piles were then measured while or after moving the bottom plate downward uniformly. The main results obtained from these model tests are as follows: 1) A kind of arching action takes place in the ground surrounding the piles, and 2) Zigzag arrangement piles are more effective than Parallel piles since a so-called double arch can be anticipated with the Zigzag piles.

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In cold and snowy areas, road pavement is greately damaged by frost heave in the ground.
This paper describes the measurement results of temperature, underground temperature, frost heaving, and soil profile obtained by field investigations (e. g. pit cutting and boring survey) at an elevation of 1750m in the Kita Yatsugatake Tateshina lava plateau.
This study led to the conclusion that fairly accurate estimates of frost heave in the field can be obtained through the use of the Segregation Potential Theory by Konrad and Morgenstern. In addition, the soil profile at the site was recorded.

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