The coefficient of consolidation is a fundamental parameter to estimate the ratio of settlement of clayey ground. When clay is improved by vertical drains such as sand drains, the horizontal coefficient of consolidation c_h is needed as well as vertical coefficient of consolidation c_v. However the rate of settlement tends to be overestimated if we use ch that was obtained by conventional laboratory tests.
In this report, a horizontal consolidation test is developed by using an improved consolidation device and a series of horizontal and vertical consolidation test is carried out.
The main conclusions are as follows:
1) The horizontal coefficient of consolidation c_h of uniform Japanese marine clay is one and a half times of the vertical one c_v.
2) The disturbance by installing sand piles reduces ch to 1/2-1/3 of undisturbed value.

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Recently, excavated roads are constructed in order to decrease bad influence on noise and landscape. But these excavated roads may induce the lowering of groundwater level because of isolation of aquifer. Therefore the prediction of change of groundwater condition due to constructing excavated linear facilites is needed.
In this paper, at first under what condition of the location of excavated linear facilities and the direction of groundwater, the isolation of aquifer occurs is studied. And a relationship between a rest rate of aquifer and isolation of aquifer is discussed. Then when the allowable degree of isolation of aquifer can not be satisfied, a countermeasure (through pipes of groundwater) for keeping groundwater level is performed. And the effect of this countermeasure is discussed.

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An analytical method that can grasp the behavior of rock masses is necessary in order to establish the rational method of design and construction control for large-scale underground cavern. In the case of underground excavation, sliding and opening of joints due to stress relaxation are considered to be the governing mechanisms of behaviors of jointed rock-masses. In the present study, a micromechanics-based continuum model of rock masses is proposed and an analytical method for underground excavation is developed. To examine the performance of the proposed method, the excavation of the Shiobara power station cavern constructed by the Tokyo Electric Power Co., Ltd. is analyzed and results are compared with measurement data. Displacement distribution, changes in tensile forces in pre-stressed anchorage bars during excavation processes obtained by the present method show accordance with measurement results.

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With the aim of reducing the construction costs of shield tunnels for gas pipelines, Tokyo Gas has decided to use a new type segment called a tenon segment. This segment differs from the standard RC segment with metal-joints as used widely in sewage tunnels in that it features elimination of the joint by using an uneven tenon between the rings. In applying this segment, safety as a structure was verified by conducting numerical analyses and various performance tests using full-sized segments. In these studies, a rational design method was realized by proposing structural analysis models enabling evaluation of structural characteristics of this segment.

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In order to investigate the infulences of initial degree of saturation and the initial dry density on the swelling characteristics of compacted Kaolin due to wetting. The observed effects of the initial degree of saturation and the initial dry density are discussed by a detailed look at the variations of the amount of swelling, swelling pressure and the degree of saturation due to wetting with elapsed time.

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To investigate the influence of soil type on collapse settlement during inundation of compacted silty and clayey soil. Compacted soils wetted under load can both swell and collapse depending on soil type, their conditions (initial dry density, initial degree of saturation) and the magnitude of the effective overburden stress. For any given set of conditions, the amount of collapse increases with decreasing the initial degree of saturation, decreasing the initial dry density, and increasing effective overburden pressure. In addition, collapse could also be eliminated by compacting the soil to a relative compaction equal to some critical value.

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Stress strain relationship associated with dynamic properties of soil have been one of main subjects in earthquake engineering field. Authors developed new technique to estimate stress strain relationship of soil from shaking table test data directly. This direct estimation technique reproduces the test condition similar to the actual earthquake loading condition.
Using developed technique we successfully obtained stress strain relationship of sandy soil from centrifuge shaking table test. The dynamic properties such as a shear modulus and a damping obtained from the model test were compared with those from traditional laboratory tests. The difference between the results obtained from the centrifuge shaking table test and the traditional laboratory test is found to be substantial.

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The porewater in unsaturated soil exists in three phases or components; the adsorbed water fixed on the surface of soil particles, the meniscus water surrounding contact points of soil particles and the bulk water occupying a part of space among soil skeletons and these water components influence on soil behavior in their own ways. This paper proposes a theoretical method for estimating the quantity of each component and quantifying their effects on soil behavior. The results of drained triaxial test on the specimens of various suction history were compared with the theoretically calculated values.

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A regional groundwater flow model of Muika-machi area in Nugata-ken, Japan, is built by an inverse analysis procedure so called the extended Bayesian method based on Akaike bayesian information criterion (ABIC). The groundwater observation data employed in the analysis is one at a steady state condition. It is illustrated through the analysis that ill-posedness which is very often encountered in this kind of inverse analysis can be overcome by introducing prior information whose relative weight to the observation data is appropriately adjusted by ABIC. The other important problem in the inverse analysis, which is model selection or parameterization problem, can also be simultaneously solved based on ABIC. The most important contribution of this paper is considered to demonstrate the effectiveness of the extended Bayesian method by analyzing actual large scale regional groundwater flow data.

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In order to propose a method which estimates the movement of shield tunneling machines simply, the authors derived equations to evaluate coefficients in mathematical models which made by the authors previously; the coefficients represent how easily the angle of the machine changes in soil. Further, the validity of the equations was clarified by analyzing experimental data of several model tests and practical tunneling data.

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Because the test conditions about the laboratory slaking test of a soft rock are decided by a standpoint of the unification and/or the simplicity, it is not clear whether these test conditions in the laboratory reflect the climate condition. Then the laboratory slaking and in-situ exposure tests used to 3 soft rocks are carried out, and 2 test results in another paper are analyzed in this study. The authors suggested two comparison methods of these test results. One is based on the representative value of the grain size distributions. The other is based on the transfer rule about the parameter of a negative binomial distribution. To apply these suggested methods to the test results of 5 soft rocks, the relation between the slaking cycles in the laboratory and the exposure time in climate are cleared.

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In order to investigate the geometrical influences on uplift behaviour of piles with enlarged base, uplift model tests of piles with enlarged base were performed in dense sand in the labolatory. The measured data and phenomenon were discussed by means of soil mechanics thories. As a result, the following behaviour has been clarified: The total shaft and base uplift capacities were varying with different enlaeged base angle. Due to enlarged base, the frictional resistance of pile shaft near enlarged base were decreased. Due to the shear dilatancy action of dense sand, the lateral earth pressure coefficients K was near K_p for dense sand, at uplift failure state.

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A methodology by which deformation modulus of geosynthetic and frictional coefficient between geosynthetic and soil could be evaluated by pull-out test was proposed. In a case of conducting a pull-out test without pulling out completely, so far, the frictional coefficient has been determined barely by method based on effective length which was estimated measuring 5 to 6 displacements along a specimen.
Proposed methodology needs only two measurements of displacement. The frictional coefficient and deformation modulus (elastic modulus×thickness) can be evaluated as a slope and a intercept of relationship between pull-out force and difference of two displacements.
Pull-out tests were carried using three geosynthetics, EPDM geomembrane and two nonwoven geotextiles with different deformation modulus. The evaluated values of deformation modulus and frictional coefficient coincide well with those from tensile test and direct shear test, respectively.

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Undrained cyclic triaxial tests followed by drainage were done on a non-plastic silt. A raelative dry density defined by ρ/ρ_max was used as a first order parameter in order to prepare consistent specimens by both tamping and water sedimentation methods. Cyclic tests were used to investigate the influences of (1) initial density, (2) particle structure and (3) overconsolidation. Based on the laboratory test results, empirical relations have been developed in order to predict the normalized liquefaction strength from the corresponding static undrained strength and the post-liquefaction volumetric strain. Both relations are found to be independent of the OCR and initial density but dependent on the initial structure formed during specimen preparation.

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This paper describes a new countermeasure for soil liquefaction proposed by the authors. The method consists of promoting excessive pore water pressure dispersion during an earthquake by temporarily lowering the water level in the vertical drains driven into sandy soil.
Two shaking table tests using a large-size axisymmetric model and a two-dimensional model were carried out in order to verify the effect of the spacing distance and the drainage condition of vertical drains. The results showed the effect of dewatered vertical drains against the soil liquefaction, and some information on the effect of drain spacing distance was obtained.

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As one of the studies on the atomization in the deep soil improvement method, theoretical and experimental studies were carried out to develop a method to estimate soil properties in real-time during construction. In the theoretical study, the resistance acting on the improving machines from the ground was studied with the soil cutting theory, and the relationship among the resistance and the ground properties was discussed. The results of the theoretical studies was examined through the field experiments and a method was suggested to evaluate the values of SPT of the ground, N values, with the loads acting on the machines from the ground. Some application of these soil-estimating methods to automatization in deep soil improvement method was discussed by determining the best operating method of the DJM machine according to the soil property estimated by the suggested method.

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A 0.8m diameter mini-drum centrifuge facility was designed and constructed mainly for the purpose of geotechnical engineering education. It was revealed that the mini-drum centrifuge is less costly, easy to use and is a versatile facility comparable to triaxial apparatus. This report describes the basic design concepts and two applications; pull out test of bell-shaped foundation, long-term modeling of leaching of clay layer, demonstrating the validity and high repeatability, the cost effectiveness of the use of minidrum centrifuge, and a potential use for long-term geotechnical environmental predictions.

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One of the authors has already defined the critical strain of rocks, which is the ratio of uniaxial strength to Young's modulus, and demonstrated that the critical strain can be used as an allowable value in assessing tunnel stability. The previous study on the critical strain has mainly been restricted to homogeneous rocks. However, we often encounter non-homogeneous rocks when a tunnel is excavated in a geologically complex ground. Thus, uniaxial and tri-axial tests were carried out in the laboratory to investigate the critical strain of non-homogeneous rocklike materials. 3-D finite element analyses were also conducted to assess the results of the experiments. In this paper, the experimental and numerical results have been presented and the characteristics of critical strains of nonhomogeneous materials have been clarified.

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