An elasto-plastic constitutive model was established in order to describe the stress-strain behavior of normally and over-consolidated sand for static loading in a wide stress region. The fundamental concept herein is based on the assumption that sand can be regarded as an isotropic material. The proposed model which involves eight parameters consists of two set of the yield, plastic potential and hardening functions. These functions are expressed based on a few basic assumptions and experimental evidences obtained from the multi-step stress path tests under 0.1MPa-10MPa confining pressure. This model can give good qualitative prediction of shear and volumetric strains for triaxial compression tests with various stress paths on normally and over-consolidated sand in a wide stress region.

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In order to analyze three-dimensional (3-D) slope stability, new 3-D methods are proposed by extending the simplified Bishop method, the simplified Janbu method and Spencer's method to three dimensions. It is shown that these methods are more accurate and reasonable than 3-D simple slice method proposed in the authors' previous study. Next, the approximate equations of 3-D safety factors for 3-D simplified Bishop method and Janbu method are presented and their limits of applicability are discussed.

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This paper presents an approximate but simple calculation method of skin friction, axial force and neutral point depth changing with ground settlement calculated results are compared with those of a field experiment on negative friction and fairly good coincidence can be seen.

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The purpose of the present investigation is to show analytically the existence of the Fenner-Pacher curve. This has been fully achieved by the distinct element method of a new model of tunneling.
The model ground consists of about 400 equal circle elements in regular array and a larger circle element of a tunnel (or circular closed lining) in the center of the array. This ground is subjected to a given initial vertical load and lateral load, and the tunneling is simulated by the decrescent of stiffness and weight of the tunnel element.
From the result it becomes clear that there are three typical characteristic curves due to the initial ground conditions: the elasto-plastic type showing continuous decrease of bearing load P with increase of deformation U_D, the Fenner-Pacher type having P_min and a stable decrescent branch of P with increase U_D, and the lateral-flow type showing sudden increase of P and/or U_D after large and unstable P_min.

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In order to investigate the relationship between frost heave phenomena and water migration in cohesive soils, frost heave tests were performed on cohesive soils under closed system condition. In addition, it was also investigated the change in frost heave characteristics corresponding to the change in the prepared soil types.
The main concluding remarks derived from these studies are as follows; i) Frost heave rates in consolidated specimens are greater than the corresponding values in compacted specimens at the early stage during frost. ii) The frost heave was also closely related with the water migration and that relationship was affected by the degree of saturation in the specimen. In addition, the change in frost heave characteristics corresponding to the change in the prepared soil types were compared and cleared.

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A reinforcing mechanism, and strength and deformation characteristics of the reinforced soil have been investigated by a laboratory element test using a small size specimen. However, the properties of soil that reinforced with a full scale reinforcing material can not be studied by the laboratory test as the size of specimen is very small.
In this paper, a series of large scale triaxial compression tests were performed in order to investigate the strength and deformation characteristics of sand that reinforced with full scale reinforcing materials (geo-grid, non-woven and metal strip for Terre armee). The tests were carried out on a dry sand sample, the results were represented by comparing the stress-strain relation of reinforced sand with that of unreinforced sand.

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An idealized double porosity model is developed for the purpose of studying the coupled effects of flow in porous blocks and fractures as well as solid displacement in saturated-unsaturated medium.
Subsequently, Galerkin formulation is used for the finite element method to develop a new technique to investigate coupled hydraulic-mechanical behavior in the double porosity model reservoir.
The verifications are performed in comparison with an analytical solution of one-dimensional consolidation problem and experimental results of unsteady flow in the sand box. Finally, a secondary compression is examined with this model, the environment of rock mass in Lugeon test is simulated, and two-dimensional consolidation problems in a saturated and saturated-unsaturated media are investigated with comparison with the single porosity model.

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An initial stress state considerably affects the stability of an underground opening. In this paper, the authors collect and arrange the data measured at 41 points in Japan by stress relief methods, and discuss the general tendency of initial stress state in Japan. The results exhibit that the magnitude of the vertical stress is close to the overlying rock weight in the most cases, however, the horizontal stress varies with directions and the magnitude of minimum horizontal stress often exceeds that of the vertical stress. The directions of minimum horizontal stresses seem to be consistent with those implied by the geodetic strains. Therefore, the large horizontal compressive stresses in Japan can be affected greatly by crustal movements.

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As well known, a shield tunnel is one of typical long structures. Its lining has many segment joints in the cross section and in longitudinal direction. For rational design of a shield tunnel subject to strong earthquake motion or ground subsidence, it is essential to evaluate its longitudinal structural characteristics accurately. Namely, effects of the joints should be taken into account in structural calculation.
This study shows approaches to evaluate the effects of the joints for longitudinal tunnel design. For this purpose, the authors present a numerical calculation model to predict longitudinal behaviour of the shield tunnel. In this model, joint elements are introduced so as to evaluate segment joints.
Compared with results of prototype test and calculation model on longitudinal behaviour of a shield tunnel, it was found that the calculation model could give results consistent with the prototype ones.

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In this paper a method is proposed for evaluating the extent of plastic zones appearing around underground openings by using displacements measured during excavations, The elasto-plastic boundary is determined by comparing the maximum shear strain occuring around the openings with the critical shear strain of materials. Both the maximum and critical shear strains can be determined by a back analysis for measured displacements.
Computer simulations using the finite element method are carried out in order to prove this proposed method. The method does not require any elasto-plastic analysis, but an only ordinary elastic analysis is sufficient.

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When geotechnical reliability analysis are performed using the stochastic finite element method, a proper estimation of the spatial distributions of soil properties is important. In this paper, to give the best linear unbiased estimator of the unknown space parameter of soil properties, the local estimation technique, which is called “kriging”, is incorporated in the stochastic finite element method so that the estimation is made based on the in-site sampling data. This paper discusses the applicability of this proposed approach using the first-order Gaussian approximation by comparing the results with those obtained by the conditional simulation for the same problem.

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In the previous paper the authors proposed the design formula for deep tunnels neglecting gravitational force. In this paper, an analytical solution for shallow tunnel under the action of gravity is presented. The assumption is taken as a cylindrical tunnel supported by shotcrete and rock bolts in a shallow elastic solid. The theoretical results are applied easily to the preliminary design method of shallow tunnel supported by shotcrete and rock bolts.

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Motivated by Ziegler's extremum principle, the author proposed a new hypothesis which leads to flow rules for granular materials as well as stress-dilatancy relationships. In this theory, the dissipation function has some specific characters so that the dissipation mechanism of friction can be taken into account. The simplest form of the function is obtained by generalizing Roscoe's dissipation energy and it gives the identical flow rule with Lévy-Mises relation for the metal plasticity. Another type of dissipation function is introduced through the microscopical consideration of frictional energy in granular assemblies. The corresponding flow rule seems agreeable with the plastic behaviors of granular materials observed through experiments in the past.

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A new permeability test is proposed which is conducted on an undisturbed sample encased in a thin-wall sampler. Two rows of small holes are drilled diametrically opposite on the side of a thin-wall tube. Water under constant pressure is supplied through the holes and fed into the soil sample to maintain a steady seepage flow in it. The seepage thus obtained makes it possible to compute the coefficient of permeability in the horizontal direction of the whole sample and to evaluate realistic mass permeability for a stratum of a soft cohesive soil with substantial thickness.

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Recently, some big reclamation projects are being pursued in offshore areas where the water depth is far beyond ten meters and there exist clay-rich soil layers whose overconsolidation ratios are not so far from unity. The present note deals with an analytical solution for the dynamic response of soil layers appearing in the offshore seabed. Referring to the result of PS-logging performed at the boring site of Senshu-oki seabed in Osaka Bay as deep as 150m, it is found that there exists a relationship between the celerity of transversal wave, v_s (m/s), and the depth of soil layers, z (m), as v_s=30z^0.5. Another informations obtained from the soil exploration also indicate that the seabed is almost normally consolidated at this site. The characteristic solution and the procedure of dynamic response analysis in such soil layers are deduced by solving the fundamental differential equation.

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