Undrained cyclic triaxial tests including drainage between consequtive cyclic loading were carried out on normally consolidated and overconsolidated undisturbed Drammen clay. Results were considered through comparison with those from cyclic direct-simple shear (DSS) tests. The following conclusions were derived from the present study: (1) On normally consolidated clays, cyclic loadieng followed by drainage may be beneficial with respect to stability and cyclic displacements. However, if overconsolidated clays are involved, the drainage effect may be unfavourable. (2) Recompression index from oedometer tests can be used for evaluating the post-cyclic recompression settlements. (3) The comparison of results from both cyclic triaxial and DSS tests suggests that post-cyclic compressibilities are not influenced by principal stress reversal and rotation.

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Three dominant factors affecting the observed uniaxial compressive strength of rocks are the inherent properties of rocks, specimen preparation and experimental techniques. Among them, we have already shown that under proper conditions of specimen preparation and carefully arranged experimental techniques, the inherent strength scatters minutely. This study focuses on the influence of the experimental techniques of the uniaxial compression test, especially, the effects of eccentricity of the loading axis in relation to the specimen's axis. The load-eccentricity relation is classified into three types which are discussed in detail. We can estimate the inherent compressive strength from the monitoring of the strains obtained from the specimen surface; even though the degreee of eccentricity greatly reduces the compressive strength. It is also indicated that there is a certain amount of eccentricity under which the inherent compressive strength never scatters. This tendency is explained from the nonlinear behavior in the stress-strain curve around the maximum stress difference.

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Loading tests are performed using various patterns of rock bolts in a 60cm diameter tunnel bored through 2.4m model ground to study the tunnel-reinforcing effect of rock bolts and establish an optimum pattern of rock bolts. Two forms of loading are implemented using side pressure coefficient of 1.0 and 0.5.
The model ground consists of low-strength sandy mortar with umaxial strength of about 1.0MPa and internal friction angle of about 25°. the rock bolts in length 10-40cm are placed at 8cm intervals with 12-48 bolts per a face.
Within the extent of the above-mentioned experiments, it is proved that the rock bolts pattern using large numbers of short bolt are effective on the condition that the total length of bolts are same.

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Proposed is methods of specifying the precompaction pressure and shear strength of compacted cohesive soils. The precompaction pressure of a compacted cohesive soil is estimated based on preliminary compaction tests. The strength gain due to the increase in precompaction pressure is not influenced by the method of compaction. Then, the strength of a dynamically compacted cohesive soil is found to be successfully estimated by knowing the unit weight and the water content of the compacted soil if data of a series of preliminary compaction-constant volume shear tests are available.

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In the present paper, we treat analytical and back-analytical methods for tunnel problems with arbitrary cross section in an isotropic elastic ground and with circular/elliptical cross section in an anisotropic elastic ground under out-of-plane shear stresses at infinity.
The complex variable method with conformal mapping techniques is used to obtain the quantities such as stresses and displacements around tunnel openings. The results of stresses and displacements at arbitrary locations in elastic rock masses are exactly computed by the given values of out-of-plane load, shear elastic constants and shape of the tunnel.
The availabilities of the back-analysis due to our treatment are examined by several numerical results.

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Current needs to bore tunnels by shield tunneling method is increasing and its application to tunnels under severer site conditions is prevailing.
Secondary lining concrete is introduced as one of prospective measures for structural reinforcement required from the conditions. On the other hand, aseismatic design for this type of structure is yet to be established.
In this paper, the behaviour of shield tunnel with secondary lining under earthquake motion was clarified by a series of structural analysis through model tests and analytical simulation. The authors have proposed an aseismatic design concept for shield tunnels in longitudinal deflection, based on the aforementioned study on the behaviour of lining concrete and the dynamic characteristics of subsurface structures during earthquake motion.

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It is very important that the soil properties of the ground where the friction piles may be placed are sufficiently affect the bearing capacities of the piles. However, for the case of the widely expanding structures such as the piers of the viaduct, it is not practical from the economical reason that the soil explorations are implemented in every points. Using the limited information based upon the soil exploration, conventional method may not accurately clarify the soil properties due to their large uncertainties. This paper proposes the probabilistic method to deal with the N-value as the random variable accounting for its spatial variation and estimates the bearing capacities for the pile foundations of the Ogori viaduct in the Kyushu expressway.

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In recent years, a horizontal drilling technique has been successively applied to embed life-lines underground. We have utilized an acoustic emission (AE) technique, as a means to detect the bit location during a horizontal drilling conducted at NKK Oogishima field. We employed the zone-location method, which provide location information in the cases that considerable attenuation exists and velocity structure is complicated.
AE signals were generated by striking soil with drilling bit.
Burst signals observed during the drilling operations were also analyzed. Arrival time sequences for the signals were determined by a cross spectral analysis. It has been revealed by the experiment that the AE source location for the burst signals can successfully be used for the detection of bit location without stopping drilling operation.

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A series of triaxial compression tests were carried out to observe the dilatancy induced by deviatoric stress. Sanjoume andesite and Kimachi sandstone are axially loaded under constant confining pressure in dry, drained and undrained conditions. Strain gauges and piezoelectric transducers are attached directly to the surface of dry and saturated cylindrical specimens to observe microscopic failure by measuring strains, acoustic emissions and elastic wave velocities. Experimental results are interpreted as follows:
1) Cracks almost parallel to specimen axis are generated by axial load.
2) Generation and/or growth of cracks is controlled by the difference between confining pressure and pore water pressure.
3) Observed inelastic contractions suggest that the internally induced stress in rock is different from measured value.

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The cofferdam was used as the temporary track when the railroad on rigid-frame bridge was constructed from the embankment. But, the actual mechanical behaviour has not been made clear and its analysis method has not been developed.
Then, we have verified to apply the finite element method, which can consider the reciprocal action of soil and structure, based on the observed data. On the releasing stress problem, the model was analyzed by the finite element method of effective stress treating soil as laminated material with modulus of deformation during decreasing load. As the results of analysis, the finite element method has been verified to understand the behaviour such as shearing deformation, sliding and reversing of the cofferdam under the biased earth pressure. But, the method cannot simulate the displacement and the stress of bar and beam elements as like the earth retaining walls and tie rods.
It was found that the fittest method was to sum up the cofferdam deformation calculated by the finite element method and the displacement of earth retaining wall calculated by the elasto-plastic model to braced excavations.

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The residual strength characteristics of a fractured zone landslide clays were examined by ring shear tests. The influence of shearing rate to residual strength was investigated. The residual friction angles φ_r′ of fifty eight clays of the fractured zone landslides were approximately 10°-30°. The residual friction angle was smaller than that of peak shearing resistance φ′ by an amount of 1°-15°. The correlations between residual fliction angles and soil index properties and gradings were not recoganized. The ring shear characteristics of clay minerals of the fractured landslide clay, vermiculite, mica, illite, chlorite and kaolinite, were investigated. These residual friction angles were about 10°-25°. The influence of particle size distribution to residual friction angle was investigated.

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Expansive soils have recently attracted increasing attention as back filling (buffer) materials for repositories of high-level nuclear waste. However, since very little has been known concerning the physical and mechanical characteristics of such materials, it is necessary to clarify the swelling and compaction characteristics of expansive soils.
For this purpose, various kinds of index tests and a series of static compaction tests were performed using several kinds of swelling soils in order to investigate the relationship between the fundamental physical properties and the compaction characteristics.

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The quasi-static mechanical characteristics of granular materials are governed by complicated deformation mechanism such as the slippage between grains and the evolution of contact points in three dimension. To investigate such micro-mechanism, a discrete element method has been developed. This method is the three-dimensional version of the granular element method proposed by one of the authors. In this paper, in addition to the general explanation of the method, an application to a regular packing of spheres was shown. The application, regardless of its simplicity, led to the results showing reasonable agreement with real behaviors of sands, which include the failure of similarity condition for the non-elastic deformation.

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It is well known that cement absorption in dam foundation grouting is strongly influenced by injection pressure. The higher injection pressure results in the larger grout take. But if a higher pressure than a reasonable one is applied, a harmful heave or up-lift will occur. Therefore, it is prerequisite to determine a rational injection pressure.
The major purpose of this paper is to propose a guiding principle of rational determination of injection pressure in dam foundation grouting, which is related to in-situ stress measured by hydraulic fracturing technique. Hence, a hydraulic fracturing procedure newly-devised by the author for in-situ stress measurement at shallow depth is also introduced.

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To investigate the influence of specimen size on unconfined compressive strength and deformation characteristics of cohesive soils, unconfined compression tests were performed on two kinds of reconsolidated remoulded cohesive soils.
The following conclusions were obtained based on the results obtained from the present study.
i) Both the unconfined compressive strength and deformation modulus increased with the decrease in specimen size.
ii) A method of accounting for the effect of specimen size on the unconfined compressive strength and deformation modulus is proposed.

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We examined the effects of the fabric of clay on its strength and deformation properties by a standard box shear test. Specimens used are consolidated clay of bentonite with salt such as NaCl and CaCl₂. The fabric of the clay is either dispersed, flocculated or aggregated structure, by estimating from the conditions of its pore fluid, that is, salt species dissolved and its concentration. It is found that the shear strength is closely related to the void ratio for its pore fluid condition and its fabric. It is shown that the fabric also affects the deformation characteristics, such as strain hardening or softening.

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