Failure process and large scale material movement of landslide, caused by the presence of a sand lens in the undercut clayey slope, at Ubilci (Yugoslavia) is analyzed by the Extended Distinct Element Method (EDEM). Magnitude of the landslide process caused by changeable clay cohesion during dry and wet season is studied for two hypothetical values of clay cohesion, high and low. The numerical results obtained are in good agreement with the failure surface and the shape of the slope of a real case landslide occurred at Ubilci (Yugoslavia).

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Stability estimation method for masonry wall by circular slip surface method is proposed. On this method, masonry wall is supposed as special soil-block system, using average cohesion and angle of shear resistance, which are calculated from stone shape and size, etc. Then based on the design method of experiments, safety factors providing various condition are calculated and disposed statistically. I could get the following results; 1) The factors effect to the stability of masonry walls and their size are: the height of slope-59%, the cohesion of soil-7.8%, the converted cohesion of wall-5.8%, the contact ratio of stone-5.8%, etc. 2) Masonry wall effect is expected in cases of H≤6.5m, c_s≤3.3tf/m² and φ_s≤25°. 3) Masonry wall safety factor is expressed as eq. (15). Above mentioned results are useful for the check of stability or decrepity of masonry wall.

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Stability mechanism of 2D and 3D slurry trenches, constructed in cohesive soil ground, were investigated by means of a centrifuge test technique which can simulate the process of excavation. Failure pattern of 2D trench was approximated by a straight line. On the other hand, collapse of 3D trench was due to the failure accompanied with the shear-band yielded by the bulge at the center foot of the long side of the trench and propagated with circular lines to the surface of the ground. The crack caused by it progressed with elliptic lines to the short sides of the trench. Using the derived failure shapes and the critical excavation depth, the 3D analysis reasonably explained the experiment results.

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An empirical equation that predicts the load distribution as well as the later deformations of laterally loaded pile groups from middle to large deformation has been derived in this paper. A new parameter αgi (factor of stiffness reduction) that considers the supperposition of the strain field in a soil layer, especially in the plastic zone, was introduced in the equation as well as the pure interaction factor αij between piles. As for the interaction factor αij, expressions based on elastict theory have been proposed by several reserches, the representative one was by Randolph. However, the test results show that under large deformation the interaction between piles was largely affected by the plasticization of soils.
The empirical equation was expressed as a function of pile internal distance, the number of pile rows, direction of load and load.
The expression was based on the test results of one kind of soils. The prediction gives good agreements with experiment data in load deformation relations and load distribution between piles.

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This paper describes the observed formation of adhesion bonds during triaxial compression tests on naturally deposited sands under high confining pressures from 1000kPa-8000kPa. The experimental results show that the degrees of particle crushing and adhesive bonding inrease with increasing confining pressure. It was also found that the degree and permanence of bonding vareid with the type of soil or soil mineral and was strongly affected by the amount of the particle crushing during shearing.

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The failure of the cut slope of weathered serpentite clay occurred. Therefore, the appropriate counterworks were conducted but the failure again occurred. In this paper, the mechanism and the cause of this faiure are clarified considering the peak shear strength and the residual one obtained from the ring shear test. The main reason of the fairue is that the differece between the peak and the residual strengths of this serpentite clay whose main minerals are a montmorilonite and a clorite is so large. The result of the stability analysis by the Generalized Limit Equiburium Method using the both strenght explains the mechanism of this failure.

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The soil hydraulic properties, coefficient of permeability and storage are essential data to predict the behavior of groundwater. Pumping tests are usually performed to determine these properties. In this paper, a new approach to evaluate soil hydraulic properties from drawdown curves which are obtained by pumping tests has been developed. In our proposed method the pattern-matching capability of a neural network is used. The neural network is trained to recognize patterns of drawdown data as input and corresponding hydraulic properties in the confined aquifer as output. The trained network produces output of hydraulic properties when it receives pumping test data as the input patterns. Drawdown data which are observed in an anisotropic confined aquifer are used to evaluate availability of our proposed method.

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In order to evaluate the rock mass in terms of resistivity, it is necessary to study the influence of resistivity of pore water and degree of saturation on rock resistivity. And also we need to study correlation between resistivity and other engineering parameters. In this paper, we made by heating rock mass models including open cracks from granite and diorite. After that resistivity measurements were carried out under various conditions. The results of experiments showed the correlation between resistivity and other geoengineering parameters and the possibility of evaluating rock mass by resistivity.

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A series of centrifuge model tests was performed in order to study the failure chracteristics of a dry sand around a deep circular shaft at the active state. Finite element analysis based on elasto-plastic model was also conducted for comparison with the experimental results. Discusion was the relationship between the failure mechanisms and the active earth pressure distributions of the shaft. It was found that the failure mechanisms of the circular shaft showed three dimensional nature and were strongly affected by the depth of ground (;stress level), resulting in different active earth pressure distributions of the shaft.

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It is necessary to clarify the phenomena of rain infiltration and the consequential effect of seepage upon slope stability, as slope failure of embankment due to rain is acompound problem of seepage and stability. The rain infiltration into embankment is influenced by soil factors such as type of soil and degree of compaction. It is also influenced by such factors as rainfall intensity or pattern and shape of embankment. These factors combine to create differences in pore water pressure, degree of saturation, even if the same amount of rain is infiltrated, and in influencing stability of embankment. Through the analyses of saturated-unsaturated seepage flow utilizing the full scale model test results, the influences of rain infiltration into embankment on slope stability under various conditions have been examined.

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Finite element analyses and model tests for excavation problems such as earth retaining are performed to investigate the influence of the mode of wall deflection and its process on the settlement of backfill and the earth pressure on the wall. Validities of analyses are checked by comparing the analytical results with the tests results of typical active and passive earth pressure problems of retaining wall. Analyses and tests in which excavation process is taken into account are carried out. Through the model tests in the present study, surface settlement, distribution of earth pressure, development of failure zone and so on depend on the deflection process of the wall. Such experimental results can be predicted well by the elastoplastic finite element analysis in which stress-strain behavior of soil is properly taken into consideration.

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Ariake clay formation, which belongs to Holocene deposit, has been classified as a uniform marine sediment by Ariake bay research group. Present study shows that this Holocene deposit should be distinguished into marine sediment and non-marine one. This paper also investigates the leaching of Ariake clay formation and finds that the leaching has been taking place lately. The high sensitivity of Ariake clay is discussed from the viewpoint of variation of salt concentration due to leaching and its effect on the geotechnical properties of the clay.

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To examine the effectiveness of a cement fixing agent method for preventing liquefaction of sand to silt deposits in relation to the characteristics of grain size of soil, liquefaction tests are performed on six cement treated soils consolidated for 1 day in a triaxial cell. Four sands and two silts are treated with ordinary portland cement (OPC) or UKC-H with cement content (C) of 2% and 5%, respectively.
It is shown that there exists a good correlation between the ratio of increase of liquefaction resistance RL for the treated soils and the effective grain size D₁₀, and that the relation depends on content of cement. Furthermore, it is found that the relationships between the liquefaction resistance and the unconfined compressive strength for the treated soils have a linearity

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Unconfined compression tests have been widely used in Japan for the purpose of determining undrained strengths of clay samples, but the unconfined compressive strengths are usually scattered even if specimens tested seem to have been subjected to the same stress history. In order to make clear the cause of scattering of the measured strengths, a series of test simulating the process from sampling to unconfined and triaxial compression test for saturated clay samples was performed with a remolded clay and four undisturbed clays, and the influence of stress release and mechanical disturbance of test specimen on the undrained strength was examined. Based on the test results, a new method for predicting in situ undrained strength of clays from the results of conventional unconfined compression test with suction measurement was proposed.

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This paper examines an estimation method of the compacted density of garanular materials by paying attention to how the compacted density of garanular materials is concerned with loose density obtained under the condition that both compacted energy and water content are zero. As a result of the large-compaction test conducted by mixing 2 types of gravel whose physical properties are different from each other and sandy soils (mountain sand), a proportionality has been noticed among the loose density of cut-grain-size distribution, compacted density, and maximum dry density. In consideration of the relation, a proposal is made in purport that estimation of the maximum dry density and the optimum moisture content is possible. Furthermore investigation has been made also with the application limitation viewed from grain-size distribution and the limit of the maximum compacted density that would be actually obtained.

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Hydraulic fracturing experiments were conducted by employing usual water injection and an urethane sleeve pressurized on a borehole. The results of experiments were compared in order to investigate effects of injected water. Fault-plane solutions of recorded AE (acoustic emission) elucidated that shear type microcracks are dominant in the both cases. However, while quick and large pressure drops with bursts of AE were observed by water injection, the pressure increased and decreased gradually with an almost constant rate of AE occurrence by pressurizing through the sleeve. This indicates that cracks extend longer and more rapidly by water injection than the case by pressurizing through the sleeve. In usual hydraulic fracturing, thus, injected water play a role to fracture and extend the crack tips. This effect obviously characterizes the mechanism of usual hydraulic fracturing.

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The distribution of soil void diameter is an important factor to express soil void structure, to select grout materials and filter materials. Air intrusion method to measure the distribution of soil void diameter is suggested. For the method based on the capillary tube model, it is required the relationship between pressure of air intruded into saturated soil and flow rate of air passed. In the present paper, the adaptability of the method is verified on the measurement of the distributions of void diameter of both sand samples and artificial capillary tube model. As a result, it is shown that the method is fairly good to estimate sand void diameter in comparison with the one by mercury intrusion method.

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A family of undrained static and cyclic torsional shear tests were carried out to investigate the effect of the inclination of the principal stress direction to the vertical axis on the wave-induced strength and deformation of dense sand. The results of the experiment indicate: (1) undrained cyclic shear characteristics remarkably depend on the principal stress direction during initial loading, (2) in undrained cyclic shear, the strength and deformation characteristics are influenced by the principal stress reversal and (3) to evaluate undrained cyclic shear strength for dense sand, we should pay attention to the phase transformation point.

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In order to investigate the lateral resistance behavior of a pile with enlarged base and the geometrical influence of enlarged base on lateral resistance behavior, lateral loading model tests of piles with enlarged base were performed in dense sand in the laboratory. The measured data and phenomenon are discussed. As a result, the following conclutions have been obtained: (1) Due to enlarged base, the lateral resistance of pile increased about 8-24%, and varied with the enlarged base angle. (2) According to the analysis of test results, at the depth x below the surface, the soil reaction p (x, y) per unit length of the pile can be expressed by the equation of p(x, y)=kx^0.5y^0.75.

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This paper examined the effect of grain surface roughness on phase transformation line and failure line under undrained torsional simple shear. To begin with, the term “normalized maximum void ratio e*_max” was defined as a measure of grain surface roughness. Then, monotonic loading test, stress control liquefaction test of constant amplitude and strain control liquefaction test with gradual increase in strain amplitude were carried out using sands of the same gradation with different surface roughness. Finally, the relationships between e*_max and phase transformation line were discussed. The test results suggest that the effects of microscopic dilatancy originated from grain surface roughness are significant on undrained shear behavior.

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Variation of tensile strength and elastic modulus of HDPE geomembrane with changes in circumstantial temperature were investigated. Two types of tests were conducted. One is laboratory tensile test, where temperature was varied from 0 to 60°C. Other is pull-out test in outdoors at temperature in the range 0 to 48°C. The data from pull-out tests were analyzed to determine the elastic modulus based on the theory of elasticity. As the results, it is founnd that tensile strength, σ_t, and secant modulus at 1% strain, E_s1, obtained from tensile tests were related with tempetature t as formulas of σ_t=23.52-0.27t (MPa) and E_s1=801.64·10^-0.0125t(MPa), that elastic modulus estimated from pull-out tests varied also with temperature and its trend coincided with that determined from tensile tests, and that Co-energy corresponding to peak stress decreased with increase of temperature.

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This study proposes a back-analysis method in which shear wave velocity and damping coefficient of soil deposit are back-calculated from the vertical accelerations measured in a dropping weight vibration test. In the back-analysis, comparison in frequency domain is made between the vertical acceleration monitored at ground surface and the ones calculated by finite element analysis in time domain. The problem is formulated as an optimization problem to find the dynamic soil parameters which minimize the sum of squares of difference between measured and calculated Fourier spectrum. The method is applied to some actual soil deposits and the result is discussed. When soil deposit is not so complicated, it is shown that the back-analyzed soil parameters duplicate precisely the actual accelerations, and that the back-analyzed soil parameters agrees fairly well with the soil parameters obtained from a conventional dynamic triaxial test.

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Strain localization is often recognized as prefracturing processes of soil and rock materials and has been extensively investigated so far. However, most of the investigations employed the classical constitutive equation, and hence the strain localization zones were found to be essentially dependent on the size of the finite elements. In the present investigation, a viscoplastic constitutive equation is generalized by introducing the strain gradient into the equivalent stress. The numerical results of plane strain finite element simulation of a uniaxial compression test on rocks are presented. The influences of the strain gradient, the finite element mesh size and the size of the specimens on the strain localization are discussed.

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