In general, the tertiary mudstone, which is classified into the soft rock, is subjected to the effect of slaking. In this investigation, in order to investigate the effects of drying, submergence and freezing on the slaking properties of mudstone, five kinds of slaking tests with various environmental conditions were performed on the parent materials of mudstone.
After various slaking tests, the measurements of pore diameter and pore volume distributions of mudstone were carried out with porosimeter apparatus. Also, X-ray analysis was performed on the mudstone subjected to the effect of slaking. The changes in pore distribution and mineral composition due to the slaking were investigated.

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In this study, the two types of test, direct shear and pull-out test, are used to evaluate the frictional resistance between geofabrics and cohesionless and cohesive soils. The results from the direct shear tests show that the friction angle between geofabric and soil depends on the soil particle size, and when the soil particle size is smaller than surface roughness of geofabric, the friction angle is almost equal to the value of soil itself. In the pull-out test, the distributions of shear stress acting on geofabric are not uniform, and the effective shear area decreases with increasing the normal stress. It is clarified that the friction properties obtained from pull-out test are equal to the results of direct shear test by means of considering the decrease of effective shear area.

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In this paper described are the test results on specimen size effect as well as specimen shape effect in the fracture toughness testing of rocks according to the “Suggested Methods for Determining The Fracture Toughness of Rock” proposed by Commission on Testing Method in ISRM. Test results for three kinds of rocks show that even corrected fracture toughness is not independent of specimen diameter, and that there exists a unique relation between corrected fracture toughness and crack extension. That is, both size and shape effects are caused by the difference in crack extension at which fracture toughness is evaluated.

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The shear strength characteristics of clay forming slip layers of fractured zone landslides are investigated by triaxial tests. The angle of shearing resistance φ′ on the landslide clay does not change with remoulding. The angle of shearing resistance of landslide clay, approximately 25°-30°, is smaller than one of marine clay in Japan. This is one of the reason which the landslide occurs at gentle slope. The value of c′ on the normally and over consolidated specimens is zero. Therefore, the main factor of landslide is the increase of the pore water pressure.
The clay minerals are investigated by X-ray diffraction method. Absorbed ions are assayed by absorptimetry. It was cleared that the gradation, clay minerals and absorbed ions have influence on the strength characteristics of landslide clay.

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Behaviour of fractured zone landslide is analysed based on the soil mechanics from a stand point of effective stress. Analysis of displacement of landslide is conducted considering the creep phenomenon of clay and the stress level at slip layer. Creep characteristic of landslide clay is investigated by the triaxial creep test. Stress level is obtained by the stability analysis considering strength parameters of clay obtained from slip surface. Relative rate of creep deformation at each stress level corresponding to each height of ground water table is calculated using the results of creep tests. The results of calculation explain qualitatively the behaviour of Nuts and Inuyose landslides.

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A series of miniature pressuremeter tests were carried out in a triaxial cell to evaluate the undrained shear strength obtained from the pressuremeter tests on normally or over-consolidated clay. To compare with these results, triaxial compression and extension tests were conducted simultaneously. Four kinds of the evaluating methods which have been already proposed were used to estimate the undrained shear strength related with the pressuremeter. As a result, the undrained strength obtained from the Stress-Strain Method, in which no functional form of stress-strain relation is assumed, was found to be in a best accordance with those obtained from the triaxial extension tests and estimated from the elasto-plastic constitutive model. Semi-Log Method which is simpler if compared with the Stress-Strain Method was found to be effective for normally-consolidated clay.

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The finite element method has been a successful analytical tool in solving various geotechnical engineering problems such as prediction of settlements. Accuracy of the finite element analysis depends on that of estimation of soil properties. However, reliable soil properties cannot always be obtained easily. Hence, an extended Kalman filter, numerical technique developed in the field of system identification, is introduced. In the course of this, the finite element technique is employed in estimating spatially variable soil properties using the observed response values. Furthermore a discussion on applicability of this back analysis method is provided.

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In order to excavate a shallow tunnel in sandy ground, it is necessary to stabilize the ground surrounding the opening and prevent a surface settlement. For the purpose, an appropriate prereinforcement should be applied to improve the ground conditions. However, it has not been fully clarified an effect and a reinforcing mechanism of the prereinforcement method. In this paper, a series of model tests was performed on sandy ground to investigate the reinforcing mechanism of prereinforcement method using steel bolts. It was found the following from the model tests.
(1) The reinforcing mechanism of bolting reinforcement is the restraint of deformation of ground by the frictional force generated between the soil and steel bolt placed in the ground.
(2) If the bolts were placed in the direction of the minimum principal strain, the effect of preventing the deformation is most effective.

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In double fracturing, in contrast to the case with hydraulic fracturing where a peak pressure appears at the point of fracture initiation, the fracture length increases with a further increases in the loading pressure beyond the point of fracture initiation. Angular distribution of tangential stress around borehole boundary then changes with the fracture length and tangential stress at the points distant from the primary fracture approaches the tensile strength there and secondary fracture initiation occurs. The double fracturing system called S-100 has already been developed by the authors, being based on the above fact. This paper describes outline of the system and demonstrates applicability of the stress determination procedure employed in the system. For the demonstration, precise elastic analyses by a Boundary Element Method, the coupled Fictitious Stress and Displacement Discontinuity Methods, were carried out for crack models in consideration of stress intensity factor at crack tip.

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A new simulation method, which will be called the granular element method, has been developed to investigate the quasi-static behavior of granular materials. The granular element method is based on an iterative process which includes the calculation of the contact stiffness matrices and the cancellation of the fixing force vectors to get the equilibrium state. The comparison with the exact solution of a granular assembly of three discs shows the efficiency of this method. Another example is the bi-axial shearing test of 122 discs. Through the detailed investigation of the results, the induced anisotropy and the dissipation mechanism are discussed. It is observed that the dissipation in granular assembly tends to take place locally before the formation of internal structure or after the collapse of the structure.

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This is a report on a study of parameters identification of mechanical constants of anisotropic rock mass and initial ground pressure from set of displacements on assumption that rock mass is anisotropic continuous elastic medium, and applicability of this method to excavation control of underground openings are also shown. A local iterated extended Kalman filter of control theory combined by Finite Element Method are applied to the parameter identification method in order to consider probabilistic feature of measured datum.
It is concluded that this identification method is effective for excavation control of underground openings excavated in anisotropic rock mass.

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Shield tunneling is used in the construction of life-line systems in urban area. Its technology has rapidly been developed but the theoretical background does not have been established yet.
Stress and displacement in linings are studied by stress function of polar coordinate, and the stability of ground is also analyzed by distortional strain energy both in unsaturated and saturated condition. The analysis shows that the distortional strain energy is the good index for supporting mechanism of shield driven tunnel.

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To study stress deformation characteristics of composite grounds, drained triaxial tests on cylindrical clay specimen with a sand column are performed. By comparing the test results with analytical values which are calculated using “SMP model” for sand and “t_ij-clay model” for clay, it is confirmed that the present analytical results by these models describe well the test results of the composite ground. On the other hand, those analyses using “Nonlinear elastic model” for sand and “Modified Cam-clay model” for clay are also performed. The results cannot explain well the volumetric change and the share of stresses. It is clarified that the evaluations of the dilatancy and the intermediate principal stress are important in analyzing the composite ground.

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The confirmation method of watertight frozen wall is an important subject to execute freezing.
A judging technique whether thoroughly waterproof frozen shaft is formed or not is suggested in the previous paper (4th. Int. Symp. of Ground Freezing in Japan, 1985).
The judging method concerning the closure type frozen wall, which has been utilized recently in a various freeze works, is described. Furthermore comparison between calculation values and observation results is carried out.

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A series of drained stress probe test on saturated remoulded clay specimens consolidated and rebounded under anisotropic stress condition was performed to investigate the influence of anisotropic stress history and stress path on the stress-strain behavior of clay. Based on the test results, a new constitutive model was proposed which could successfully describe the stress-strain behavior of anisotropically lightly overconsolidated clay.

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In order to elucidate the mechanism of permeation by short gel time grouts, we investigated the effects of injection pressure P', injection rate q, injection time t, and gel time Gt on the solidified shapes. Through a lot of injection tests using the large injection apparatus, we obtained the following conclusions. 1) Permeation without fracturing is possible as long as P' is increasing during injection. 2) If the permeability of sand is large enough, the succesive grout can permeat spherically by perforation in the pore gel at the solidified part.

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Descrived is a numerical procedure to back-analyze the non-linear constitutive parameters for joint elements in simulations of particular discontinuities occurring in sandy ground during tunnel excavations. In this paper, hyperbolic stress-strain relation is adopted in the direction tangent to the joint. Thus, with observed initial displacements in an earth tunnel excavation the proposed procedure enables to make predictions of future settlements and the safety factor against failure. Firstly, the proposed procedure is verified with hypothetical case studies. Subsequently, the procedure is applied to actual case studies and comparisons are made with analysis results based on parameters obtained in laboratory experiments.

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The present paper describes the theoretical aspect of the determination of the stresses in rock unaffected by a borehole with an instrumented cylindrical inclusion which was established by one of the authors (Hirashima). The stress fields of the elastic matrix (isotropic or anisotropic) containing a solid cylindrical inclusion are discussed and the formulae to be used in practice to determine the stresses in rock are presented. The results of calculation by Hirashima's theory and Amadei's theory which has been published recently, are shown by several numerical examples.

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This paper aims to analyze stability of parallel tunnels on each stage of tunneling, to make clear the relations between stability and various physical values of ground and support. The stability of parallel tunnels is descussed from the point of distortional strain energy by stress function of bipolar coordinates. The preliminaly design method of parallel tunnels supported by shotcrete and rock bolts is presented. The results are applied to actual data of parallel tunnels, and then the relations between elastic constant of ground at the front tunnel excavation and that at the rear one is proposed.

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Experimental studies show that local earth pressure acts on existing shield tunnel, when open cutting or shield tunnelling is performed nearby.
The aim of this paper is to present a numerical method of a psudo-three dimensional analysis of segment rings under patch loading.
The present method is based on the following assumptions:
1) Behavior of shield tunnel in the longitudinal direction is analogous to that a simple beam on elastic foundation.
2) Cross-sectional deformation of segment rings under patch loading can be approximately estimated by the cylindrical shell theory.
In view of these assumptions, the longitudinal rigidity of shield tunnel can be replaced by the equivalent spring constant related to the longitudinal deflection.
As a result, bending moment of segment rings with staggered joints is obtained through analyzing circular beams of two ring model supported elastically by the spring.

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Unsaturated soil can be simulated to elasto-plastic material. Based on the test results of suction controlled triaxial test on compacted kaolin clay, theoretical initial yield function and subsequent loading function are induced. Then the theory is examined by stress-probe test. In this paper triaxial stress state is defined by three stress components, they are, effective average principal stress, p=σ_m-u_a, effective suction stress, f(S)=χ(u_a-u_w) at failure condition, and deviator stress, q=σ₁-σ₃, in which u_a and u_w are pore air and pore water pressure, respectively. Only one loading function similar to Original Cam Clay is obtained from the theory, on the other hand, results of stress-probe test indicate the presence of additional yield surface like failure surface besides one theoretically predicted.

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Information about liquefied and not-liquefied sites during past earthquakes is useful for liquefaction potential mapping of wide area. Therefore, inquiry of liquefaction-induced ground failures during the Kanto earthquake was performed for preparing a liquefaction potential map in Tokyo lowland. Interviews with above 300 persons who had experienced the hazard in Tokyo lowland were carried out. Historic liquefaction-induced ground failures are determined from these narratives and the reports concerning the earthquake. Liquefied sites distribute along the rivers and old river beds, and in reclaimed lands. Not-liquefied sites distribute away from the coast or rivers. Liquefied grounds along the rivers consist of sandy deposits containing only a small amount of fines, and the grounds containing considerably fines hardly liquefied. However, the sandy deposits containing fines were prone to liquefaction in reclaimed lands.

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This paper is concerned with the factor analysis of a boulder-fall by the theory of quantification and the presentation of a method for evaluating the possibility of the boulder-fall on a slope. Based on the considerations about the topographical, geological and mechanical conditions related to the phenomenon of boulder-fall, detailed field investigations have been carried out on many actual slopes in Yamanashi and Nagano prefectures. The statistical analysis of the data obtained from the field investigations is conducted to grasp quantitatively the degree of the influence which each of the factors gives to the phenomenon. Moreover, on the basis of the theory of quantification, the method by which the possibility of an outbreak of boulder-fall can be estimated is presented, and its applicability is examined through comparing with observations.

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This paper presents results of model tests in the laboratory and the numerical analyses by the kinds of static and dynamic method carried out as a series of the research on the seismic stability of a large scale slopes. As these results, it is clear that the failure mechanisum of slope between pseudo-static inclination test and dynamic test using shaking table differ and the circular arc slip method gives the severest assessment in the kinds of analyses of seismic stability. In addition, the relationship between the seismic coefficient of pseudo-static test and the acceleration of dynamic test is evaluated quantatively and it is proposed to use the equivalent seismic coefficient obtained from the response equivalent acceleration of slope as seismic force for seismic stability evaluation by static method.

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In this study, the characteristic of equivalent seismic coefficient and the applicability of the design seismic coefficient of a large cutting rock slope arround Nuclear Power Plant were examined by analytical parameter survey. As the results, the equivalent seismic coefficient by dynamic analysis become great with increase of transverse elastic wave velocity and the case of long period motion. That is, as the wave length of rock mass become longer, the equivalent seismic coefficient become great parabolically. Moreover, there is a inverse proportion relation between the ratio (dynamic safety factor/static safety factor) and wave length. In addition, the graph to forecast the dynamic sliding safety factor under the input seismic motion of the max. acceleration 500gal from the result of static simple method was proposed and the applicable range of design seismic coefficient of rock slope was indicated.

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The present paper discusses two main subjects. The first one is concerned with a method for the evaluation of ultimate bearing capacity in which the updated data obtained during the in-situ loading tests are used. The new evaluation method of applying the residual settlements with the total settlement in each loading step is proposed. The other is to show the improved equations of ultimate bearing capacity which are determined based on the statistically analyzed data on many proto-type loading tests done in the fields. The results are compared with the values given by the methods generally used in Japan and the engineering usefulness of the new methods are emphasized.

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The distribution of earth pressure acting on buried rigid pipes measured for centrifuged models of 42 cases was compared with FEM elastic analyses, which yielded results that conformed to the test results in most cases, showing that the earth pressure acting on buried rigid pipes is affected predominantly by the lateral and bottom boundary conditions in the ground and by the interface boundary condition between pipe and soil. This conclusion made clear the interrelationship among the following several studies of the authors on this problem conducted in this decade: a field test, centrifuge model tests, and an analysis based on elastic theory. The difference in earth pressure among three types of pipe installation in actual construction, ditch type with sheet-piling, ditch type without sheet-piling and embankment type, was concluded to be due to the difference in the lateral boundary condition in the ground.

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Variational stability analysis is a new method that can determine the safety factor as well as the critical sliding surface which satisfies the kinematical constraints. Theoretically it can be applied to nonhomogeneous problems, however, its use is scare because of the difficulties in analytical application. A well known variational stability formulation may be of Baker et al., but there are some controversy with its application. At first, we pointed out the variational approach affords the extremum by discussing on the equality of the method to the upper bound calculation. Then we developed a numerical code based on Baker's theory and examined its applicability to the slope stability and compared the results with some of the conventional limit equilibrium methods. It is concluded that results of variational method agree quite reasonably with those of Spencer method and is proved to be more practical for less time consuming.

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It has been unusual to utilize foamed cement (FC) for embankment fill materials, which has been conventionally used as a matrix of lightweight concrete. The FC reported by this paper was produced with the porosity n=80-90% for the purpose of using as lightweight fill materials because of its dry unit weight γ_d≈0.3gf/cm³. To mke clear mechanical properties of FC, unconfined compression tests and tri axial compression tests were performed. This paper describes about these results, which are summarized as follows. (1) Unconfined compressive strength of FC firmly correlate with void ratio and water content after curing. (2) Compressive yield stress is inversely proportional to effective confining pressure.

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Using an ordinary circular shield for construction of double track railway tunnel, the cross section becomes larger than the net required section. As a result, the construction work takes not only more cost but also longer time. The multi-circular face (MF) shield tunnelling has been developed to mitigate these problems, and can build a tunnel with a special cross section comprising multi-circles partially overlapped.
In this study, the experiment is executed to make clear the basic behaviors of double-circular face shields (one with two faces aligned horizontally and the other with faces aligned vertically). The results show that the cutter torque and total thrust force of the MF shield are smaller than those of a circular face shield to construct the same double track railway, and that the MF shield has good characteristics in the stability of a cutting face and in its maneuverability.

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This is the report of an experimental study on the stability of tunnel face driven by shield, including the “caving phenomenon”.
The caving is called the initial slip failure of ground along the face produced by the cutter disk of shield. From the results of experiments, the followings are summed up: (1) the caving occures prior to the general failure of the face ahead of the shield. (2) The ground strength necessary to prevent caving is larger than that necessary to prevent general failure (3) the larger the diameter of shield, the greater the ground strength is needed to prevent caving.

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