Plane strain compression tests (CD-test, σ_x=σ_x0=const.) were performed on Toyoura sand specimens measuring 9×8×5cm. The initial stress conditions of these specimens varied within the range of 100≤σ_z0≤300, 25≤σ_y0≤500 and σ_x0=100(kN/m²-unit). The following results were obtained: (1) The initial stress conditions are divided into three groups according to the specimens' dilatancy during initial stress loading; (2) Stress paths and stress strain relations under plane strain compression are classified into two or three groups corresponding to these groups; (3) Strength parameter is unique irrespective of the initial stress conditions.

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In order to understand the deformation of “railroad ballast”, which is a component of the ballasted track composed of crushed stone, the simulations of full-scale track tests regarding its part as an assemblage of coarse granular materials were performed in this paper. And the applicability of discontinuum analysis to the cyclic plastic deformation of railroad ballast was discussed in comparing analytical results with DDA (Discontinuous Deformation Analysis) and experimental results. As a result, some new guidelines for the application method of DDA were indicated, and the cyclic plastic deformation of railroad ballast was proved the fabric transformation of particle alignment accompanied by sliding between particles in terms of the mechanics of granular materials.

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Since 1960's, many methods to evaluate the stability of slurry trench walls have been proposed. However, there are no reliable and general methods developed due to the complicated nature of the problem. In this paper a new 3-D limit equilibrium method to evaluate the stability of slurry trench walls is proposed, which considers the importance of lateral confining forces acting on a sliding soil mass, that has not been considered in the past. The proposed method is applied to results of a centrifuge model test on a slurry trench constructed in sandy ground and compared with analytical results by the 3-D elasto-plastic FEM. This shows how applicable the proposed method is to sandy ground.

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Ring shear and reversal box shear tests are conventionally used for measuring the residual strength of soils. In this paper the normal stress, the overconsolidation ratio, the shear displacement rate and the change in the normal stress during the shear process are considered among many factors affecting the test results. It was shown that the residual strength obtained in a low range of the normal stress should be interpreted based on the properties of the direct shear test apparatus. The residual strength is almost constant to the change in the overconsolidation ratio, but it changes in relation to the shear displacement rate, depending on the type of soils. The stress paths of the soil specimen which have once reached the residual strength move along the residual strength line accompanying the change of the normal stress.

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Based on the assumption that the deformation of a landsliding mass is small enough compared with the displacement of the mass, many analytic procedures to presume the shape of underground slide surface have been proposed. Several parts of the old procedures are improved in this paper. First, to presume the complicated slide surface, combination of polynomial functions representing partial slide is examined. Next, to raise the accuracy of presumption, the concept of data weight is introduced into the least square method. Effect of these improvements is verified by numerical analysis applied to actual landslide area, Narao district, Nagano prefecture in Japan.

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In order to investigate the rate effect on cyclic shear characteristics of clays with various plasticity, a series of undrained cyclic triaxial compression tests has been performed applying cyclic loads with various frequency. Firstly, the effect of frequency on the development of excess pore pressure and axial strain was investigated. Then the relation of axial strain against effective stress ratio was correlated by the cyclic load frequency.
As the major work of the present study, the cyclic shear strengths of clays with various plasticity were investigated and formulated in terms of plasticity index and load frequency. As a result it has become possible to evaluate the cyclic shear strengths of soils with various plasticity and initial stress condition subjected to various frequency of cyclic loads.

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This paper reports on design method of bridge foundation against ground flow caused by liquefaction. This method allows us to estimate the displacement due to ground flow by FEM analysis and to design bridge foundation. We verified the design method using the past case histories of damage caused by earthquakes, including Hyogo-ken Nambu Earthquake, and we also examined the applicability of the design method to the ground in Tokyo area. Moreover, this design method can be applied to design countermeasures against ground flow for existing bridge foundations.

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A method is proposed to estimate settlement of breakwater, for which mound foundation failure occurred during high wave storms. It is shown that this settlement depends on height ratio of high wave to critical wave, as well as the shape and period of high wave. Failure probability of mound foundation is calculated as large as 50-60%. However, the expected settlement of breakwater due to this kind of failure is estimated about 59-75cm. Such a degree of settlement may not damage a breakwater disastrously.

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This paper presents the theoretical investigation of the spatial distribution of hydraulic conductivity in a stratum that is considered to be geologically homogeneous and proposes a methodology of numerically generating more realistic nonuniform homogeneous ground. It was shown that the hydraulic conductivity of the numerically generated ground was always lognormally distributed. Moreover, the power spectrum of a spatial variation of the hydraulic conductivity resulted in nearly 1/f type. The analysis of flow in the generated grounds show that even if the grounds are geologically homogeneous there exist locally predominant flow paths as commonly observed in natural groundwater flow.

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Dynamic centrifuge model tests were conducted to simulate the seismically-induced displacements of sheet pile quay walls, in order to understand the mechanisms of lateral ground flow of liquefied soil behind walls and to evaluate the effects of the lateral-flow earth pressures acting on pile foundations. It was found that the tests could virtually reproduce the actual lateral -flow of ground caused both during earthquakes and post liquefaction; the influence of earthquake acceleration was very large for the residual displacement of pile foundations; the lateral-flow earth pressures acting on foundations were considerably smaller than the value calculated in the Specifications for Highway Bridges; the degradation ratio of young's modulus of liquefied soil was 1/650.

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The pre-lining method has been applied in a shallow overburden or a soft ground tunnel to prevent surface settlement and stabilize cutting face. The pre-lining is the auxiliary method in which arch-shell linings are formed ahead of cutting face prior to excavation. However, design of this method is not established sufficiently. This paper describes the results of model test and full-sized test to investigate effects of reinforcement for the thin flexible pre-lining. As the results of model test, it is clarified that the pre-lining is effective for face stability and surface settlement. And quantitative estimation method for face stability is proposed.

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We had developed a super large scale direct shear test apparatus (SL-DS) with the specimen of 160cm in diameter and 80cm in height to investigate the characteristics of stress-deformation relations and strength on coarse-grained soils contained large size particles.
This paper introduces the mechanical structure of SL-DS as well as tests results on sand and mass-soil (a coarse-grained gravely soil composed of weathered granite rock). The test results show the angle of internal friction obtained from the direct shear test is approximately equal to that obtained from triaxial compression test, which may prove the usefulness of this apparatus in practice.

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The authors have studied the liquefaction characteristics of decomposed granite soil called Masado. Masado is reclaimed ground material on Kobe artificial island, which liquefied during the 1995 Hyogo-ken Nanbu earthquake. To evaluate liquefaction resistance of soil from ductility viewpoint, the energy dissipation capacity obtained from cyclic triaxial test under strain controlled condition was used. Comparing the energy dissipation capacity of Masado with that of fine clean sand such as Toyoura sand, it was found that the energy dissipation capacity of Masado has a small dependency on its relative density comparing to clean sand. It was also found that fines existing around coarse soil particles play an important role on liquefaction resistance of soil.

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In order to discuss causes of abnormal stress relief curves obtained in over-coring stress measurements, the authors classified 267 stress relief curves into four patterns. Consequently, the authors found that two of the four patterns reflect stress condition and should be used for stress determination, while the other two do not. One of the two abnormal stress relief patterns was most likely caused by existence of cracks in rock or improper gauge setting condition. The other one was found to be caused by temperature change due to cooling water in coring, when difference in temperature between the water and rock exists.

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When a structure with spread footing is built on soft ground, the ground under the structure deforms, and the relative settlement accompanied with the deflection of the foundation occurs. The purpose of this paper is to investigate the factors related to the rate of relative settlement. Numerical results of finite element method with an elastic/visco-plastic model as a constitutive law and measured values of settlements of an existing structure are used in searching the factors influencing the relative settlement. It was found that countermeasures of increasing the permeability in the horizontal direction of the ground under the structure significantly reduce convergence time of the relative settlement.

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In order to obtain effect of relative density D_r, pile diameter D and depth z on p-y curves of single pile in sandy ground, a series of divided pile loading tests and single pile loading tests were conducted in geotechnical centrifuge. Relative density D_r, centrifuge acceleration ratio n and model pile diameter D were selected as test parameters. It was found that obtained p-y curves from divided pile loading test could be modeled by hyperbolic p-y curves and single pile loading tests result could be reasonably simulated by the hyperbolic model. The applicability of bi-linear p-y curve were investigated by comparing with test results. Finally, method of evaluation on the coefficient of subgrade reaction k_hi and and ultimate subgrade reaction p_max were proposed.

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Structures constructed on soft ground have often suffered from serious problems related to large ground deformation. Load reduction or strengthening surrounding soil may be effective countermeasures against these problems. This paper deals with numerical analyses of an existing embankment which have suffered from these problems since the beginning of construction, and where reduction of embankment load by EPS was made. This paper reveals the difficulty to estimate the current situations and the degree of safety of structures even detailed observation and numerical analyses were made. The paper also shows the difficulty to predict future behaviour of structures after maintenance work, and that this issue should be more focused by engineer.

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Lateral loading tests on pile groups of four and nine piles arranged on square grids were performed using a model ground of cohesive soil, which resulted in large deformation of piles. In addition, lateral loading tests on a single pile were also performed in order to clarify the efficiency of pile groups. Based on the results, the load burden ratio for each row of grouped piles was calculated, and the large lateral deformation behavior of the piles was studied. It was found that the group of four piles was more significantly affected by the ground strength than the group of nine piles. Furthermore, empirical equations to derive the efficiency of pile groups were proposed based on the footing displacement ratio, number of piles in a group, and relative rigidity between the ground and piles.

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Indicator simulation technique is one of the most useful methods to grasp heterogeneity of the permeability of the ground. In this paper, the several covariance matrixes which are needed in this method, and the different scattergram between the permeability and the soft data are examined. By using the resistivity tomography and the fracture density as the soft data, the interference tests are simulated and the responses at the observation points are compared to examine the accuracy of the model. The followings are found as the results: the best prediction is given by the model using calculated covariance matrix, even if the weak correlation between the permeability and soft data are used.

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A series of undrained cyclic triaxial tests were performed in this study on sand-gravel materials with different particle gradation and different relative density. Despite large differences in particle gradation, a good agreement in the liquefaction strength was obtained for specimens having the same relative density. The post-liquefaction undrained strength, also measured after each liquefaction test, was much lager for gravelly soils than that for sands having the same relative density. Empirical correlations were made between the liquefaction strength and the SPT N-value or S-wave velocity, which indicate that, for the same N-value and S-wave velocity, gravelly soils tend to exhibit smaller liquefaction strength than sands.

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It is well-known that the mechanical behaviors of rock joints due to shearing generally are heavily dependent on the their geometrical condition, which is so-called roughness profile. Therefore, it is inevitable factor to evaluate the effect of roughness profile on the shear behavior. Up to now, many researchers have proposed the formulations, which associate the shear strength with roughness profile of rock joints, under the idealized assumption that no change of the configuration of joint surface due to shearing occurs. From these viewpoints, focusing on the geometrical change of joint surface due to shearing, this study proposes the formulation of shear strength based on digital data of roughness profile.

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The pile tip levels, which are the foundation levels of piled structures, are correlated with the ground surface levels from the geological point of view. We had proposed before the estimation method which is based on the cokriging procedure and had produced excellent results. This paper presents the new estimation method of pile tip levels taking account of not only the ground surface levels but also the elastic wave exploration data. For the purpose of preventing from increasing of model parameters, the ground surface levels are treated as the trend component. In this paper, the proposed method was verified using the numerical data and applied to the actual data.

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Various types of reinforced retaining walls have been recently developed and adopted. On these retaining walls, however, effects of frost heaving damage prevention measures have not yet been clarified. In this study, a full scale model of a multi-anchored retaining wall was installed in the field, and measurements were performed over four winter seasons. Following results were obtained; 1) measured freezing fronts were associated with measured freezing earth pressure on facing blocks; 2) earth pressure on facing block repeated seasonally between 40-50kpa in winter and 5-10kpa in melt season; and 3) the effectiveness of thermal insulation material and frost-nonsusceptible backfill against frost damage was evidently recognized.

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This paper presents a example of the soil stabilization to prevent the slaking of gravely mud-stone soil as embankment material on-site fill in construction of Terre-Armee reinforced earth wall embankment. A series of compressibility tests and unconfined compressive tests were carried out to investigate the effect of cement stabilization to prevent the slaking of gravely mud-stone soil.
The results shows that the settlement due to the slaking of mud-rock soil is controlled by the addition of cement stabilizer. A series of pull-out shear tests in laboratory and field also were carried out to investigate the pull-out frictional characteristics of strip plate of Terre-armee method in compacted mud-stone soils.

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When one evaluates the shear strength of rock joints in detail, the investigation based on both mechanical and geometrical condition should be considered. As for mechanical conditions, shear behaviors of rock joints is affected by loading condition. As for geometrical conditions, shear behaviors of rock joints should be heavily dependent on the configuration of rock joints, which is so-called roughness profile. From these viewpoints, the authors have developed both the apparatuses measuring both the shear strength and the roughens profile of rock joints. This paper describes the history of the developed apparatus and their applicability.

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