A series of cyclic undrained triaxial shear tests were performed in this study on unsaturated sand materials with different fines content. According to the cyclic loading triaxial tests, cyclic undrained shear strength considerably increased as the degree of saturation decreased. On the other hand, the cyclic undrained shear strength of unsaturated sand reduced as the fine content increased from 0% to 20%. It was clarified in this research that, when non-plastic fines were mixed in sand, cyclic undrained shear characteristics largely changed independent of the degree of saturation. Hence, it is important to evaluate the influence of fines fraction on the undrained strength properties appropriately.

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  The mural paintings in the stone chamber of Takamatsuzuka Tumulus have been seriously damaged because of the appearance of various fungi on the lime plaster wall of the chamber associated with the intrusion of insects. It was then decided to dismantle the chamber and evacuate the mural paintings from such uncontrollable environment in soils. Far from archaeological investigation, dismantling of the stone chamber and lifting and transferring of the chamber stones require the practical senses of stability assessment of the excavated walls as well as bearing capacity of the foundation for crane frames that are used for lifting of the chamber stones. On the basis of the assessment, the excavated mound of Takamatsuzuka Tumulus is found to have enough strength to lift the dismantled chamber stones. The necessary and feasible supporting system in terms of earth retaining walls has however been adopted to avoid the unexpected harmful ground movement due to the exisitence of earthquake induced cracks and fissures that have been found in the whole tumulus mound. All dismantled chamber stones have successfully been transferred to the preservation center and being under restoration.

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  Assessment was made of the creep properties of sodium silicate-grouted sands. A simple measuring method of the creep upper yield value was also examined. Sodium silica grouts used for this experiment can be divided into the following three types. One type is grout that gels when placed in an alkaline condition, and the second gels in an acidic condition. The third is a colloidal sol grout that increased the particle by polymerization. We researched the creep properties of these grouts. As a result, the structures of gel did not influence the creep upper yield value of grouted sand. However, the difference of the gel structure which differed in the type of grouting material affected the creep fracture time of grouted sand. The short term increment method can be used as a simple measuring method to obtain the creep upper yield value.

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  The Discrete Element Method (DEM) with microscopic numerical model of fluid flow is applied for simulating fluidized debris flow to examine the effect of excessive pore water pressure. The model uses a two-way coupling scheme, that is, the model solves fluid pressure in void spaces surrounded by particle elements used in the DEM to consider compressibility of fluid by particle movement and fluid flow across the void space by pressure difference, on the other hand, the calculated fluid pressure is applied for particles involved in the void space as a body force in proportional to occupied area in the void space. Also, the scheme uses a grid-generation method with advancing-front technique to update boundary fluid-grids automatically during calculation. Numerical simulations are conducted to mimic a simple fluidized debris flow, which was done by lab-scale test. The results are compared with experimental data of lab-scale test, also simulation result of dry condition and different permiability. As a result, it is clarified that the microscopic fluid flow model represents localized pore water pressure under dynamics of particles, and is a useful tool to analyze fluidized landslide and debris flow.

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  To investigate the discontinuous behaviors of rock slopes/masses after collapse of the rock slope caused by the earthquake, the discontinuum based approach is necessary. In this study, the earthquake response analysis for discontinuous blocks was performed by Discontinuous Deformation Analysis (DDA) with a single block and multilayer block models. The results obtained from the simulations by DDA were compared with the analytical solutions and results from the laboratory shaking table tests. We investigated the applicability of DDA to seismic problems. It was found that DDA is powerful tool to analyze seismic response for both simple block and multilayer block models.

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  Coal fly ash-water mixtures show flocked state, viscoid state and fluid state. In this study, the effects of water mixing ratio on its strength properties of slurried coal fly ashes were investigated by conducting triaxial compression test. The strength properties of slurried coal fly ash strongly depend on water mixing ratio. It was clarified that the optimum water mixing ratio exists for mobilizing shear strength. The consistency indexes proposed by the authors are useful for estimating the optimum water mixing ratio. And the simple quality control method by the fall cone test is proposed to set the optimum water condition of coal fly ash.

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  The bending yield strength of the frozen soils decrease with salt concentration. The effects of salt on the yield pressure of the circular plates which modeled the frozen soil walls to be mobilized at the starting and/or arriving portals for the shield machine operation was studied. The bending tests on the circular plates of saline frozen soils were carried out in order to determine an approximate relationship between the yield pressure and salt concentration. On the saline frozen clay, the approximation method which had been confirmed the availability at the non-saline frozen soil agreed satisfactorily with the experiment. However on the saline frozen sand, the experimental values of yield pressure were larger than the estimated ones. The reason was investigated using the caluculation by the finite element method and the shear strength of the saline frozen sand.

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  Ryukyu limestone layers are sufficiently competent as a bearing stratum for shallow foundations. However, because a number of cavities exist in the Ryukyu limestone layers, foundation design is not always straightforward. The effect of cavities on the bearing capacity characteristics of strip footing was examined by model tests. The model ground was made by cement-mix-silica sand, simulating typical mechanical characteristics of a Ryukyu limestone. Detailed observations focused on the development of failure mechanism, as well as load intensity and settlement relationship. Upper bound analyses using failure mechanism deduced from the experimental observations, provided the general trend of the effect of cavity on bearing capacity.

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  The authors develop a numerical code based on Local Discontinuous Galerkin Method for transient groundwater flow and reactive solute transport problems in order to make it possible to do three dimensional performance assessment on radioactive waste repositories at the earliest stage possible. Local discontinuous Galerkin Method is one of mixed finite element methods which are more accurate ones than standard finite element methods. In this paper, the developed numerical code is applied to several problems which are provided analytical solutions in order to examine its accuracy and flexibility. The results of the simulations show the new code gives highly accurate numeric solutions.

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  A freezing index was estimated from five kinds of probability distribution models. The results showed that it could not be represented by a only distribution model, but good matching was found to a lognormal distribution and a normal distribution. Thus, an estimation method using the largest 1/3 of the figures picked from the data was studied. The freezing index obtained from this method was compared with the actual value, and this demonstrated high accuracy. The effects of the number of data on freezing index estimation were studied. As a result, data for more than 25 years were found to be necessary to estimate the freezing index, because change in that for the period before the 1990s was very large.

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  Embankment and cut slope collapse due to heavy rainfall along railway lines takes a variety of scales, which need to be predicted to determine effective measures for prevention. There are many embankments and cut slopes along railway lines, therefore it is necessary to predict the scale of collapse by using results of simple investigations. Accordingly, we carried out statistical analysis of many past collapse examples and developed a method to predict the scale of embankment and cut slope collapse. This method predict the collapsed soil volume by using conditions of embankment and cut slope obtained for results of simple investigations. This report gives this method.

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  When a steel pipe in installed into a ground in the pipe roof auciliary tunneling method, an overbreak excavation by expanding bits and friction cutters is carried out since friction and drag around the steel pipe's surface and on joints between the steel pipes must be reduced. Consequently, spaces around the steel pipe are generated and settlement might be caused in a small overburden condition. In order to clarfy the charactertics of the surface settlement by overburden and to propose the control method of surface settlement, in this paper, the modeling apparatus of overbreal excavation has been developed and the several cases of modeling expereiments have been also performed. With considering two factors, namely, overburden and overbreak ratio, in the experiments, the surface settlement has been discussed. Based on the experimental results, the contsraction method of the pipe roof which controls the surface settlement as much as possible has been proposed.

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  The use of shallow stabilization and floating-type cement-treated columns has been developed as a method with accepetable settlement for maintaining the proper functioning of high standard roads or high embankement on soft ground. So it is most important to predict total settlement for this type of improved ground. In this study, consolidation properties of this type improved ground were clarified by the field observation results obtained from two kind of full scale test embankments. Further, a method for predicting the total settlement for this type improved ground with respect to the improvement parameters is proposed. Its validity is confirmed from field observation results.

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  Desaturation of ground by air injection attracts considerable attention in resent years as an innovative technique for liquefaction countermeasure. This technical report describes an in-situ air injection test which aims to confirm an effectiveness of the air injection to desaturate ground and validity of observation techniques to monitor the evaluation of unsaturated area. In the test, air was injected from an air injector set at a depth of 6m. Air flow rate increased linearly with increasing air injection pressure and desaturated area was formed within 4m from the injector. 3D resisitevity tomography and FDR probes were found to be effective to detect evolution of the desaturated area.

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  The tuff gravel transported from the midland of Kobe city was used for the reclemation work at Kobe Airport, which was constructed offshore about 8km distant from the Kobe city center. In this project, the compressive defomation of the submerged embankment during the reclematon work was measured by means of a newly developed instrumentation equipped with a pressure guage. The system is capable of measuring automatically the vertical deformation of the reclaimed land by using the radio system. The rate of volume change during the reclamation work below and above the sea-water level was manifested. The applicability of this monitoring system was successfully demonstrated for the case of rapid reclemation work in deep sea and on poor sea-bed conditions.

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