In this study, a sophisticated numerical model incorporating a hardening-softening constitutive model with shear band is calibrated from the direct shear test results, and validated for the prediction of the behaviour of medium dense Fotainebleau sand bed for quasi-static displacement induced by reverse fault's base rock with dip angle of 60°. The vertical displacements profile of the ground surface, minimum vertical base displacement for the rupture to reach the ground, the average dip angle propagated into the soil as well as the horizontal extent of the deformed surface ground due to different stress fields (centrifuge and 1g tests) are evaluated by having close agreement between experiments and numerical analyses.

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Slope failures frequently cause labour accidents in construction sites. It is also known that even a small collapse can cause serious injury to workers. The Short Pipe Strain transducer (SPS) was developed to measure increments of shear strain in the shallow section of slopes, and then its applicability was investigated by Centrifuge model tests and Prototype model tests. Clear increases in the responses of strains (r_s) were measured with progress of slope cuttings in the series of tests prior to failure. In particular, creep strain curves were observed in loam ground. A couple of minutes could be provided by monitoring either 2nd or 3rd creep. Accordingly, it was confirmed that SPS does not only measure the slope movement but also senses an increase of the potential risk of slope failure.

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Electromagnetic emission is one of the most dramatic and most intensely studied manifestations of earthquakes. However, there is great confusion and even greater controversy among the previous reports because it seems nearly impossible to imagine that such diverse phenomena could have a common physical cause. In this study, electromagnetic noise contained in radio wave (AM) was detected and analyzed prior to earthquakes. It was found that noise level is gradually increasing and then decreasing before an earthquake. Maximum noise level was commonly observed one to two weeks before the earthquake.

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In Japan, there are many mountain districts, and land use around the steep inclination area proceeds remarkably, in addition, because of much rainfall, many land slide disasters occur every year. The limit rainfall curve in which variables are unit time rainfall and accumulation rainfall is proposed as an index of the land slide risk in rain. But, the limit rainfall curve is decided uniquely regardless of the ground condition.
In this study, in order to establish the prediction method of slope stability in rain, 2 dimensional FEM analysis in which input variables are the total and unit time rainfall and the soil permeability was done. The method which decided the limit rainfall curve that a slide safety factor became 1 was proposed by neural network that regress the input variable and the safety factor in non-liner shape. And we quantitatively evaluated the influence to the safety factor by the inconstant rain in which unit time rainfall changed.

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A conceptual model, accounting for pressure and free-face dissolutions, is presented to follow the evolution of fracture permeability in granite that was observed in a flow-through experiment. This model addresses the two dissolution processes at contacting asperities and free walls within fractures, and also describes the multi-mineral dissolution behavior, showing a capability that the evolution of fracture aperture (or related permeability) may be followed with time under an arbitrary temperature and pressure conditions. Predictions utilizing the model proposed in this study show a relatively good agreement with the experimental measurements, although the concentrations predicted underestimate the actual.

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In the DDA (Discontinuous Deformation Analysis), the ratio of velocity energies (squared velocity ratio) is used for the energy loss during collision. The velocity ratio is investigated in detail with the experiments. It was clear that the velocity ratio is dependent on the incident velocity of the normal direction. Therefore, velocity ratio is not appropriate to consider the property as a direct input value of the simulation. However, we have clarified that it is possible to perform a rockfall simulation by considering the velocity-dependence of the velocity ratio in the application of DDA by using the “Scale Factor” as proposed by Pfeiffer et al. (1989).

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In the case of construction of repository for nuclear waste near the coastal area, the effect of brine on hydraulic conductivity and swelling pressure of bentonite as an engineering barrier should be considered because these characteristics are affected by salinity of water. Thus, the effect of salinity of water on hydraulic conductivity of bentonite has been conducted experimentally. However, it is necessary to elucidate and to model the mechanism of the phenomenon because various kinds of bentonites may possibly be placed in various kinds of salt water with various degree of salinity. In this study, a model for evaluating hydraulic conductivity and swelling pressure of compacted bentonite is proposed considering increase in number of sheets of montmorillonite crystal because of cohesion as well as decrease in viscosity of void water. Quantitative evaluation method for hydraulic conductivity together with swelling pressure of several kinds of bentonite under brine is proposed based on the model mentioned above.

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The effects of bentonite kinds and dry density on the settlement behavior of overpack for high level radioactive waste disposal were investigated using both experimental (i.e. centrifuge) and analytical approaches. The nonlinear elastic analysis using a tangent modulus of elasticity obtained from the diffuse double layer theory was carried out to explain the settlement behavior from centrifuge experiments. The difference of properties between bentonites can be considered by this analysis. The results of nonlinear elastic analysis agreed with experimental results. The amount of settlement was decreased with an increase in the dry density and was exponentially decreased with an increase in the swelling pressure. Furthermore, no difference of the amount of settlement was observed if swelling pressure of each bentonite is same. When swelling pressure is more than 1 MPa, the amount of settlement of model overpack into bentonite with 400 mm thickness was less than 10 mm.

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A high-resolution geological survey by high frequency seismic wave has been developed. This method is designed to transmit a pseudo random wave of desired frequency. We can measure an accurate geological structure between wells separated by a long distance. We conducted this new method to locate a firm siltstone accurately for the pile foundation work of multi-storey car park in Chubu international airport. Accurately visualized image of the firm siltstone layer enabled us to design exact lengths of the pile foundation. We compared the actual cost of the foundation work with the cost estimated by designing based upon only boring log and found that we saved 40% of cost of foundation work by this new method.

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Some mountain tunnels suffer from deformation and cracks caused by earth pressure. This deformation might progress along with the time passage for some tunnels. Because of uncertain points of such time-dependent deformation and destruction behavior of a mountains tunnel, a maintenance management method has not yet been established currently. In this study, we focused on tunnels deformed due to earth pressure, and tried to apply a numerical analysis using the ground strength reduction model to them. As the result of the study, we have mainly obtained four outcomes. Firstly, we realized to simulate the behavior of tunnels deforming as time goes by. Secondly, by choosing appropriate ground strength reduction curve, we could express wide-ranging progress of displacement. Thirdly, we could evaluate the effect of countermeasures for deformation appropriately. Last, we could determine the most appropriate time for carrying out the countermeasures.

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In late years, environmental protection is regarded as an important issue in a field of the ground improvement by the chemical grout permeation. As the part, the authors push forward the study of a new grout (We call it biogrout as follows) which used microbial metabolism and silica colloid. In this issue, we hereby report that we have developed a new grout which has almost same gel time and strength as those of a conventional grout by using silica compound and microbe even if volume of an agent for pH adjustment in grout is comparatively less.

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This study evaluated an uplift behavior of circular and square anchor foundations in dense Toyoura sand, by comparing a model test with 3D FE analysis. The model tests were performed by taking the value of h/D as two. The 3D analysis was an elasto-plastic model in which progressive failure with shear band effect was introduced into the constitutive equation. The 3D analysis was able to predict the uplift behavior in both circular and square anchor foundations. The uplift resistance in circular anchor foundation was smaller than in square anchor foundation in case of having same D. The scale effect was recognized and the degree of the scale effect was similar in both anchor foundations.

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Newmark method is used for the analysis about seismic displacement of the sliding block which occurs to the slope. As for this method, the precision of the analysis becomes bad because it is computing as the rigid body though sliding block moved as the elastic-plastic body. The purpose of this paper is to analyze the displacement of sliding block and that adopts the dynamic FEM which is used for the analysis of the elastic-plastic body and the vibratory conveyance theory which computes the displacement of the rigid body. This new method was named “the elastic-plastic vibratory movement theory”. As the result of experiment on the vibration with the model slope, it was found that the precision of this new method is higher than the conventional theory.

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Fracture size distribution in rock mass should be estimated objectively and theoretically based on in-situ observations because large fractures often cause rock engineering problems, such as water inflow and rock deformation in underground facilities. Therefore, probability density function (PDF) of trace length was derived theoretically in this study based on a relationship between trace lengths and size distribution of fractures on an assumption that fracture sizes follow powe-law distribution. Thus, the derived PDF enbled to estimate fracture size distribution from trace length data which are observed directly on in-situ observations.
In addition, the authors applied the derived PDF to some trace length data at construction sites in Japan in order to estimate radius exponents and minimum fracture sizes.

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The characteristics of probability distributions and geometries on discontinuities such as fractures and faults in rock mass generally dominate mechanical and hydrogical features of geosphere. In this paper, the authors construtcted Discrete Fracture Network (DFN) models for a fractured rock mass based on the probability and statistical methods which were focused on relationships among obtainable fracture data from results from in-situ investigation. Additionally, the authors conducted a comparative study focusing on the fracture intensities which were obtained from DFN model based on the method and theoretical relationships among fracture data. The results of this comparative study shows that the fracture intensities and even their standard diviations from both methods have high-consistency.

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In order to examine the long distance propagation mechanism of environmental ground vibration which is made in a viaduct section, a field measurements was performed for this viaduct in which the vibration problem actually generated. The experiment with a model using the similarity rule in a gravitational field and two-dimensional FEM analysis were enforced to examine this mechanism. From these considerations, On the supporting layer and the surface layer, some part of the low frequency vibration was propagated to the long distance without the damping property by a distance from the vibration source.

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In this research 2D finite element analyses have been carried out for simulating the real field data of braced excavation. In the analyses elastoplastic constitutive model, named subloading tij model, are employed which can describe typical stress deformation and strength characteristics of soils. The ground mainly consists of soft and sensitive clayey soils together with some sandy soils layers. The numerical analyses have been performed considering all details of the field conditions such as the construction sequences, different soil characteristics, soil-water coupling condition and other important features of the excavation site. It is revealed that the analyses can properly capture wall displacement, surface settlement and deformation mechanism of the ground.

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In the present paper, a water-soil coupled elasto-plastic finite element analysis method has been proposed for unsaturated river embankment by incorporating unsaturated soil-water characteristics. The simplified three-phase method has been developed based on the multi-phase porous theory by assuming that the compressibility of pore air is very high. It is shown that the proposed soil deformation-seepage flow coupled analysis method is applicable for simulating the behavior of river embankments during seepage flow. The method has been verified by simulating experimental results of seepage flow and one-dimensional flow problem. Then, using the proposed method behaviors of river embankments with different initial saturations and different permeability coefficients during the high river water level have been numerically analyzed. From the numerical work, seepage-deformation characteristics of river embankment, the effects of permeability, and the initial saturation have been clarified.

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Takamatuzuka Tumulus, having found in 1972 at Hirata, Asuka village in Nara Prefecture was built with mural paintings in the stone chamber around at the end of 7^th century or at the beginning of 8^th century. Because of the appearance of various fungi on the lime plaster wall of the chamber associated with the intrusion of insects, the paintings have been seriously damaged. It was then decided to dismantle the chamber and evacuate the mural paintings from such uncontrollable environment in soils. A series of laboratory tests is conducted on undisturbed samples of the compacted earth materials called “Hanchiku” from the mound of Takamatsuzuka Tumulus to evaluate the physical and mechanical properties of them because these parameters are indispensable for evaluating the stability of the mound that has to support the crane base to dismantle the chamber and lift the stones out of the Tumulus. In situ non-destructive test such as needle penetration test is also carried out to know the in situ strength of the mound. In the present paper, the structures of the Tumulus mound is reported based on the investigation and the physical and mechanical characteristics of the compacted earth materials from the Tumulus mound are discussed.

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In this study, compression properties of mudstone soils distributing in Maizuru city were investigated focusing on disintegration features of soil particles. Slaking tests and single particle crushing tests were curried out in order to know the disintegration characteristics of the mudstone soils. And compression behaviors of the mudstone soil under saturated condition and dry condition were obtained from one-dimensional compression tests. As a result, it was clarified that due to the collapse of soil structure and the decrease of single particle crushing strength caused by submergence, the compression yield stress becomes lower and large settlement occurs.

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The surcharge technique is one of highly effective and economical means for accelerating consolidation and reducing post-construction settlement. This paper is concerned with one-dimensional consolidation analysis taking account of the removal of surcharge. A series of laboratory consolidation tests are made on two normally consolidated organic soils to confirm secondary compression behaviors after the removal of surcharge. Based on the laboratory investigation, a method of estimating the amount of secondary compression is proposed empirically for practical use. One-dimensional consolidation analysis is described for predicting the consolidation-time curve before and after the removal of surcharge. Satisfactory agreement can be obtained between the computed results and oedometer observations.

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A non-linear elasto-plastic relationship of geomaterials is presented incorporating the Coulomb's criteria, in which cohesion and angle of friction mobilized on the shear band are expressed as functions of plastic shear strain. A procedure is developed to decide these functions by analyzing the results of triaxial compression tests. The scale effect of geomaterials caused by localized deformation within the shear band is taken into account by using a smeared crack concept in FEM analysis. Finally, this FEM code is used for simulating the triaxial compression tests on specimens of different sizes and the bearing capacity problems of a foundation adopting meshes of different sizes. The results show that the load-settlement curve and localized defomation in the ground can be computed with reasonable accuracy using a larger finite elements than the speciment from which the geotechnical parameters are determined.

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In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore the gas migration tests are conducted in this study to investigate the mechanism of gas migration. On the basis of the experimental facts obtained through the gas migration tests, possible gas migration mechanism and a model for calculating breakthrough gas pressure are proposed.

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Freeze-thawing phenomena of the ground occur due to temperature variability in the cold districts. It is important to understand mechanical characteristics of the ground subjected to freeze-thaw sequence. In order to investigate the deformation properties of volcanic coarse-grained soil in freeze-thaw process, a series of cyclic triaxial test for determining defomation properties were performed on specimens with artificially freeze-thaw cycles. The results showed that freeze-thaw sequence effects a change in deformation properties, especially G₀ of volcanic coarse-grained soil. The main reason is attributed to increase of finer content and change of pore structure caused by freeze-thaw sequence.

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The behavior of discontinuity, which includes fault and joint, existing in rock mass is considered to give the great effect on the deformation and stability of surrounding rock mass during excavation of large-scale underground cavern. In this paper, the excavation simulation and stability evaluation are carried out by using distinct element method (DEM). The geometrical distribution of joints is also considered in the modelling based on the geological investigations and modified according to the new observation during the cavern excavation process. The numerical analysis indicated that the joint orientation around the cavern influences the deformational behavior and stability significantly.

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Excavated slopes become safe only when they are either excavated to a safe slope angle or when protective measures are taken. During slope cutting work, slopes are at greater risk of failure. In many cases, slope failure suddenly occurs without any warning signs and the workers do not have time to escape and hence accidents take place. To prevent such accidents, the mechanism of slope failure caused by slope cutting work should be clarified. In this study, field tests of slope excavation were carried out. As a result, it was found that in all cases spalling or local failure of the excavated slope was observed before the slope failed completely. This mechanism is consistent with some accidents due to slope failure during slope cutting work. Because the horizontal and vertical movements could be measured during the field test, it is possible to predict the movement of the slope just before failure.

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