This paper describes the vane shear strength characteristics of ultra soft clay ground during self-weight consolidation in centrifugal flight. A series of vane shear tests is carried out in the laboratory floor after centrifugal flight. An effect of stress relief in the process from centrifugal field to gravity field on the shear strength is also discussed.
As a conclusion, the relationship between vane shear strength and water content of its part of clay ground is unique during the self-weight consolidation. Applying the equivalent effective stress to the test results of laboratory floor, the relationship between vane shear strength and effective stress is equivalent to that of centrifugal field.

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The effects of cutoff walls surrounding a buried structure for mitigating damage of its floating up due to soil liquefaction are discussed. Centrifuge model tests results showed that floating up displacements of the structure with cutoff walls were very little although the one without cutoff walls was very large, and the displacement of the structure with cutoff walls were directly influenced by a thickness of liquefied ground under the structure. Static analysis presented for the design of a cutoff wal1 showed good agreement with the centrifuge tests results.

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In recent years, finite element method (FEM) has been widely used in deformation analyses of geotechnical engineering field. Although FEM made large-scale simulations possible by the improvement of computer performance, it needs a great labor to divide a domain analyzed into finite elements as the scale of the problem becomes larger. Moreover, the results strongly depend on mesh configuration when dealing with liquefaction and the following ground flow phenomenon. On the other hand, the mesh free method has claimed the attention of many researches because this method provides a technique for descretizing an analyzing domain without conducting the mesh division. In this paper, the element free Galerkin method (EFGM), one of successful mesh free methods, is applied to numerical analysis of liquefaction and the ground flow phenomenon using the fluidal elasto-plastic constitutive equation. The set of equations for the equilibrium and the continuity of pore water is derived and its discretization in space based on the EFGM is formulated for small strain and finite deformation analyses. In order to assess the effectiveness and accuracy of the proposed procedure, some numerical simulations are conducted.

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It is difficult to evaluate the characteristics of volcanic ash soils accurately by indexes which represent properties of the soil. There are also no available indexes to evaluate the frost-susceptibility of volcanic ash soils. In this study, we carried out various physical property tests and frost heave tests for 47 kinds of volcanic coarse-grained soils distributed widely in Hokkaido. It was revealed that a lot of vocanic ash soils evaluated as frost-susceptible by the conventional iginition test are not frost-susceptible by a series of these test. We also showed that the frost-susceptibility of volcanic ash soils could be evaluatued easily based on the relationship between the natural water content and the optimum water content of them.

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In this study, the seismic behavior of the retaining wall consisting of concrete panels and backfill reinforced with geogrids is evaluated based on the dynamic elasto-plastic FEM. A series of shaking table tests and a test construction of retaining wall of a real scale are performed for the verification of the analyses. Based on the above, a rational analytical technique for seismic evaluation of retaining walls reinforced with geogrids is proposed.

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A multiscale analysis model for fissured material bodies, which incorporates a frictional contact analysis of cracks in microstructure, is proposed. Based on the saddle point theorem using Lagrange multiplier method, the frictional contact analysis in micro scale is reasonably formulated, and therefore its computational algorithm is constructed along “active set strategy”. The proposed model simulates a plate loading test and a block shearing test on a cracked rock mass model and can predict gradual increase of apparent stiffness and shear strength of the rock mass due to crack closure during loading. These predictions are in good agreement with such phenomena observed in actual rock mass tests and assure usefulness of the proposed model in rock mechanics.

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The application of clean-water sludge, generated in the water-treatment processes of water service, as a geomaterial was examined. A design California bearing ratio test was conducted to assess the use of the sludge as a subgrade construction material for subgrade and back filling applications. The improvement effect of mixing a decomposed granite soil into clean-water sludge is larger in terms of decreasing the water content than in increasing the strength. The application of sludge as a subgrade material or base course material was examined by a modified CBR test. If clean-water sludge is appropriately dried and a decomposed granite soil is added to it, the sludge can meet quality requirements for other than the base course by simply reducing its water content to less than 100%. Adding a decomposed granite soil further increases the improvement effect.

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Recently there has been considerable interest in anomalous transport in porous media. An advection-dispersion equation (ADE) is widely used as governing equation of contaminant migration, however there have been a number of reports that ADE does not express observational and experimental data. This clear discrepancy is attributed to little knowledge about a mechanism of anomalous transport. The primary purpose of this investigation was to clarify the mechanism of anomalous transport analytically. In addition, a method, which predicts contaminant migration not only in homogeneous material but also in heterogeneous material, has developed by combining the clarified mechanism and streamline method. The result obtained from the developed method has agreed well with experimental results of this research.

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To examine the effect of the fabric anisotropy of sand and clay on the quasi-elastic modulus, the shear wave velocity in three different directions was measured by the bender element method on specimens with different fabric anisotropy. In addition, the Young's modulus was measured by cyclic triaxial test on small strain and monotonic loading test. Test results showed that; 1) the initial shear modulus obtained from the shear wave for propagating and vibrating parallel to the bedding plane is higher than the other two kinds of moduli, 2) the Young's modulus in the horizontal direction, E_h, is higher than that in the vertical direction, E_v, 3)the anisotropy of elastic modulus in NSF clay is more considerable than that in Toyoura sand in this study.

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While the long facebolting method has become widely used in mountain tunneling as a stabilization measure of tunnel faces, its reinforcing effects have yet to be quantitatively estimated. In this paper, the in-situ measurements are conducted at a tunnel site to investigate the behavior of facebolts installed at a tunnel face. Three-dimensional numerical analyses are successfully performed to simulate the measured behavior. Furthermore, the parametrics study on the cohesive properties of the bolts with ground has shown that the restraining effets of the face extrusion are significantly affected by the cohesive properties that exhibit different magnitudes and distribution patterns on the induced axial forces.

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K₀-consolidation tests using the triaxal testing apparatus on undisturbed peat and organic clay were conducted and in situ tests by the flat dilatometer were performed on peaty soft ground in Hokkaido, to investigate the coefficient of earth pressure at rest of these soils.
This study has revealed that the K₀-value of normally consolidated peat and organic clay decreases with an increase in their ignition loss. The K₀-value of over consolidated peat and organic clay depends strongly on OCR as compared with mineral clay and then “m”value increases with their ignition loss. In case of estimation of K₀-value using the flat dilatometer, the equation proposed by Iwasaki has relatively applicability for peaty soft ground.

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Shear strength of rock joint is affected not only by rock strength and sliding friction, but also by joint asperity shape greatly. In this study, the shear strength of rock joint was found to be exhibited by piece wise linear criteria based on geometric information on joint asperity shape, through the mechanical consideration on failure mechanism of joint by using the upper bound calculation in limit analysis. Based on the consideration of failure mechanism of rock joint, the method by Rengers (1970) was applied to estimate the geometric information on joint asperity shape. It made the strength parameters of piece wise linear criteria to be determined objectively based on the joint asperity shape. Applicability of proposed model was made clear by comparison with both analytical solutions of upper bound calculation and experimental results on rock joints. Concerning the scale effect of strength by sample size and the anisotropy of shear strength to depend on shear direction, the applicability of proposed model was examined through the case studies.

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A series of drained monotonic loading and cyclic loading tests were performed under a constant effective mean principal stress, in order to investigate the effect of the principal stress axes rotation on the particle breakage of a volcanic coarse-grained material using a hollow cylinder torsional shear apparatus. On consolidation and monotonic torsional shearing processes, the experimental results showed that the particle breakage could be estimated not only by the effective stress ratio but also by the principal stress axes rotation and its angle. However, under the cyclic torsional shear process, the particle breakage was affected by the consolidation condition. It is also pointed out that the continuous principal stress axes rotation might produce certain increase in the particle breakage. In addition, the amount of particle breakage in the cyclic torsional shear test can be evaluated by a total plastic work calculated from the time history of the stresses and the strains.

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For the geological disposal of high level radioactive wastes, an excavation damaged zone (EDZ) adjacent to the tunnels will be the potential pathways for radioactive contaminant transport, having a high hydraulic conductivity due to the fractures in a rock. The potential pathways will be sealed by the engineered barriers, that is, a combination of tunnel plug, backfill and grouting, the material for which would be a clay-based mixture upon consideration of the long-term stability of the seals. Clay-based grout is one of the effective method to interrupt the migration of radionuclides through the EDZ.
The application of clay-based grout using bentonite to sealing the EDZ was tested around the tunnel in the granitic rock and the modeling of a reduction of permeability was carried out based on the results of the in-situ test. The filtration model of bentonite slurry could describe the results of the in-situ test and the modeling indicated that there was the most effective concentration to reduce the permeability of EDZ.

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Steel pipe sheet pile reinforcement method for existing caisson foundation in water, which is driving SPSP around caisson foundation and connecting between SPSP and caisson at the top, is proposed. This method is constructed in practical, but effect of reinforcement and SPSP load ratios, which refers to the total load transmitted from caisson to SPSP reinforcement divided by the total load applied on the SPSP reinforced caisson, is not understood. It is thought that these factors are influenced by caisson-SPSP connection condition and flexural rigidity ratios of caisson to the SPSP and bearing layer's condition. To make these influence clear and recommend easy, cheap and effective construction method, centrifugal tests on these factor are conducted.

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In order to reinforce the technology for grouting a fracture in a rock mass, the process of grouting in a borehole to grout a fracture was visualized in a model test. The test revealed the following points. (1) Grouting of a fracture in a rock mass is greatly by clogging in the intersection part of an injection hole and a fracture. Clogging at the intersection between the borehole and the fracture in particular causes grout flow rate to be reduced with time even the condition of fixed pressure. (2) The phenomenon is largely ascribable to the effects of coarse particles and aggregated materials with a larger diameter than the fracture width that are contained in cement grout in minute quantity. (3) Grout flow rate is related to the width of the fracture, injection pressure, and grout mixes. (4) Screening the grout is effective for preventing clogging.

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This paper proposes a reliable method for estimating Mohr-Coulomb strength parameters c and φ from a load-displacement relationship obtained by plate loading and borehole loading tests. Strength parameters c and φ are back-calculated so that those minimize the difference between measured and calculated displacements which are based on a hyperbolic type of stress-strain model. The incremental method for non-linear stress-strain analysis and the simplex method for optimization are respectively employed. It is possible to estimate c and φ separately from a load-displacement relationship usually measured by in-situ test since c and φ affect the load-displacement relationship in a different manner.

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In order to examine the influence of viod ratio, and grain size distribution to the unsaturated shear strength of sandy soil. Conventional triaxial compression tests were performed for saturated and unsaturated sandy soil specimens with different initial void ratio, 50 percent diameter, and uniformity coefficient, Based on the test results, the in fluence of these properties to the shear strength increment to the increase of suction were made clear as follows. With the increase of initial void ratio and 50 percent diameter, the shear strength increment becomes smaller, while the shear strength increment becomes larger with the increase of uniformity coefficient which gives largest influence to the shear strength.

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The present study was performed to confirm the applicability of granular coal ashes to the reclamation material with proper resistance against liquefaction during earthquake. A series of cyclic triaxial tests was carried out on specimen of granulated coal ashes to evaluate the liquefaction potential under various confinig stresses and relative denslties. Granulated coal ash was subjected to cyclic triaxial tests, and the results were compared with those of natural sand, to examine the cyclic shear properties of the material. The results revealed that the cyclic shear strength curve of granulated coat ash was gentle under confined pressure, but it was still higher than the cyclic shear strength curve of natural sand. It was also observed that granulated coal ash undergoes remarkable particle crushing. In addition, it is therefore assumed that particle crushing that occurs at the time of consolidation contributes to the stabilization of the structure to deliver high cyclic shear strength, while particle crushing that occurs at the time of cyclic shear contributes to the generation of axial strain to reduce cyclic shear strength.

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The bond strength of rock bolt must be evaluated appropriately for design of tunnel support. In the present study, the pullout tests were conducted in order to obtain the bond strength of various rock bolts, which includes higher stiffness or fiber-reinforced plastics (FRP). Especially, the bond strengths of various rock-bolts in early age were evaluated. From the test results, the bond strength of steel rock-bolt in different mechanical properties was almost equal. The different materials were so influenced factor on the bond strength of rock bolt.

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Long facebolting, as an auxiliary method in mountain tunneling, is used not only for the measure of face stabilization but also for the measure of preventing surface settlement. In this paper, the mechanism of preventing the surface settlement by means of long facebolting is investigated for shallow tunnels using three-dimensional numerical analysis. It is found that the facebolting words effectively in sandy ground resulting from the confining stresses in the ground ahead of face reinforced with the long facebolts.

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A method of identifying the impulse response by TSP(time stretched pulse) is applied to bender element test. From a series of experiments with sand, it is shown that the impulse response of bender element test system can be given by this method and the received wave form closely resembles to that obtained in the case square input wave is transmitted. Two kinds of shear wave velocity, for travel time and for phase difference in frequency domain (phase velocity), are obtained from impulse response. It is observed that shear wave velocity for travel time is close to that given by square input wave. Phase velocity, on the other hand, changes with frequency, and strong dispersion of velocity dependence on frequency is implied.

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A series of undrained cyclic triaxial tests was performed on sand and clay mixture. The samples were prepared by mixing silica sand and marine clay with six kinds of mixing ratio. The tests were carried out under both isotropically and anisotropically consolidated condition. The liquefaction was observed in the samples with fines contents less than 9.8% in which the pore pressure developed up to initial confining stress. While the cyclic strength for isotropically consolidated samples was monotonically increased with increasing fines contents, that for anisotropically consolidated soils decreased With increasing plasticity index. The cyclic strength for anisotropically consolidated sample with Fc=19.6% shows the largest value among them because both sand particles and fines matrix contributed to mobilize the strength. The stlength became similar for the samples with fines contents greater than 30%.

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