The cylindrical specimens with three different dimensions, 100mm, 75mm and 50mm in initial diameters, were trimmed from the undisturbed samples of peat. These specimens were set in triaxial apparatus and then were isotropically consolidated under different consolidation pressures. Also, after isotropic consolidation, drained compression shear tests were performed under constant lateral stresses. After the end of isotropic consolidation and drained shear tests, the measurements of the changes in shapes of cylindrical specimens were carried out with digital dial gauge. In the case of peat, unevenness is remarkably observed in the surface of specimen with the development of compression. In order to represent quantitatively the state of irregular surface of specimen, unevenness ratio was defined. The effect of unevenness on the shape of specimen is increased with the increase in consolidation pressure and the decrease in specimen size. It was indicated that the change in shape of specimen due to the occurrence of unevenness almost corresponded to the distributions of organic matter content and water content in specimen. Moreover, based on the calculated values of typical parameters of stresses and strains, the method for obtaining the crosssectional area after consolidation was discussed on the cylindrical specimen of peat.

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Nabetachi-yama tunnel under construction in Niigata Prefecture is being paid much attention to, since the ground surrounding the tunnel is proved to contain high-pressured gas which is supposed to be a main cause of a considerable amount of deformation during the tunnel excavation. However the interaction between the rock skeleton and the contained gas was hardly clarified so far. The aims of the present paper are to make a simple mechanical model for such a rock mass under the gas-trapped condition, to simulate the tunnel deformation by an axi-symmetric finite element analysis and finally to investigate effective countermeasures against a large amount of deformation.

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Focusing on slope surface of railway embankment, we discussed the spatial characteristics of soil strength in the railway direction using the autocorrelation coefficient, which is expressed as a function of soil strength in the slope surface. It becomes small at high soil strength and large length between soundings. We statistically analyzed shapes of embankments which occurred to rainfalls. Then we proposed a more reasonable interval of sounding point which corresponds to the autocorrelation and the collapse width of embankment slope.

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As a method to investigate loosened regions around a rock chamber, the authors took note of the measurement of small strain changes in rock due to stress redistribution resuiting from the excavation of a chamber. Then, they examined the applicability of it through a laboratory experiment, with examining the applicability of the monitoring of acoustic emission and P wave velocity. Moreover, on the measurement of small strain changes, they made a new gauge and measured real strain changes in rock with excavation of a small chamber. Through these laboratory and in-situ investigations, it was elucidated that the measurement of small strain changes is applicable to investigate loosened regions around a rock chamber.

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In this study, a technique called geostatistics is applied to some geotechnical problems. Geostatistics, which has been used to estimations of ore grade distributions in mines, is a kind of statistical estimator technique on the assumption of spatial correlation of estimated variables. Such variables are called regionalized variables.
The problems analyzed in this study are estimations of spatial distributions of thickness of layers and resistivities in layered sedimentary rock mass using data from 37 boreholes. The rock mass is in the part of Tono mine area in Toki and Mizunami City, Gifu Prefecture, Japan. The analyses make successions in interpolating data from site investigations on mathematical background, and establish the ability of application of geostatistics to geotechnical engineering problems.

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The diaphragm cutoff walls have been lately adopted for foundation treatment of embankment dams constructed on alluvial deposits. It is significant for the engineers in design and construction of diaphragm wall to take into account of structural behaviors during earthquakes. This paper studies the statical and dynamical interaction between diaphragm wall and surroundings in above type of dams and their stability by means of numerical analysis on TADAMI dam. especially clarifies the effects of rigidity of diaphragm wall on their stability through comparing the behavior of whole structure in the case of bentonite concrete wall with the one in the case of conventional concrete. Besides, the characteristics in dynamic behavior of diaphragm walls of both materials are clarified through both in-situ vibration tests and their numerical simulations as well as the validity of the seismic response analysis applied to this studies are confirmed.

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The diaphragm cutoff walls have been lately adopted for foundation treatment of embankment dams constructed on alluvial deposits.
The stability of embankment dam with diaphragm cutoff wall depends upon the structural behavior of contact part between the top of diaphragm wall and dam body. Thus, comprehensive studies on the behavior are indispensable, neverthless reasonable methods for structural analysis to the problem have not fully been established yet. This paper proposes the analytical method for evaluating earth pressures acting on the top part of diaphragm wall of embankment dam and confirms its validity through the comparison of predicted values with measured values on the various points at TADAMI DAM.

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In order to assess the tunnel stability by estimating the lining stresses with a small number of field measurements of displacements, two formulations of back analysis are newly proposed theoretically. The formulations are; (A) A method to minimize the square of external forces acting on tunnel lining, (B) A method to minimize the energy given to the tunnel lining from the external forces. The accuracy of the methods is investigated through parametric study by a finite element method on two dimensional elastic lining. Application of the methods to a lining with several types of external forces shows appropriateness of it. When 6 components of input displacements are given to the method (A), high accuracy with a few percents error on displacements and less than 20 percents error on the maximum shear stress is also confirmed.

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This paper described new generalized governing equation associated with groundwater behavior considering physical properties of wide range of porous media from soil material, soft rock to hard rock based on Biot's two phase mixture theory. Through the investigation of physical meaning of each term constituting the generalized equation, physical effect on the feature of groundwater-flow by means of interaction between volumetric strain of porous media and pore water was made clear, and from an engineering viewpoint, a new criterion is proposed, which clarifies the applicable methods to various type of design of seepage problem.

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This study investigated the methods to predict future consolidation settlement based on the observation at a site under construction. A new type of model concerning the influence of secondary consolidation and the settlement-time relationship was proposed. This paper also examined a way to identify the unknown parameters of various models including the model by the maximum likelihood method. This paper proposed two methods to select the most accurate type of prediction from many models in the period of settlement observation. These methods were applied to an example of actual observation, and was confirmed to be useful for the settlement prediction.

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A series of centrifuge tests with a reduced model by factor of 1/13.3 was performed using undisturbed block samples of scoria, containing gravel size particles to attempt direct comparisons with large-scale in-situ loading tests. It was found that centrifuge models predicted yield loads to be 85-93% of corresponding prototypes, and elastic deformations close to the prototypes. It was also seen that in the models, clear slip lines were not developed, and settlements at yield load were much larger than those in prototype. It was inferred that the two observations may be due to particle size effect.

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This paper discusses the consolidation settlement prediction based on the observation at the site under construction. Since it is difficult to estimate the effects of the embankment load, the observed settlement data during the period of embankment work has not been used for the future settlement prediction. However, it is necessaly to complete a new technique which predicts the settlement in the early stage of observation, and feeds back the result to the design. This tequnique will satisfy a fixed construction period and will save construction cost. This paper proposes a new method to predict the future settlement in the early stage of observation using observed data during the period of embankment work. It will also describe a new way to feed back the result to design. These methods are applied to some actual observations, and this paper showed the process of analysis concretely. The result indicates that these methods are effective and useful.

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The stress-strain behavior of soils which have intermediate properties of sand and clay depends on the properties of the particles and it grain size distribution. The mechanical properties of sand and clay have been investigated in detail. However the mechanical properties of sand-clay mixed soils have not been sufficiently clarified. In this study, a method for predicting the stress-void ratio relationship of sand-clay mixed soils is proposed by taking into consideration of soil structure. The soil structure is regarded as consisting of skeleton of corse particles and matrix constituted by fine particles and water. The stress in the mixture is evaluated by using the strain energy of the mixture. The stress-void ratio relationship and coefficient of volume compressibility of the mixtures are derived by using the proposed method. Its validity is confirmed from the experimental results of two types of the mixtures.

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A numerical method by FEM is proposed in order to analyze the consolidation of composite ground improved by sand piles such as sand compaction pile method. The proposed method takes into account the stiffness of piles and the drainage through sand piles which is called ‘vertical drain effect’. This method can express the influence of decresed permability in smeared zone. Then composite grounds having such properties are analyzed by the proposed method with ‘Multi-link element’ which is a quasi-three-dimensional FEM for composite ground. Consequently the proposed method describes well the influence of diameter and pitch of pile on consolidation degree. The distribution of safety in ground and the change of stress share accompanying pore-pressure dissipation are also obtained.

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It is well known that rock bolts are extremely effective for reinforcement of jointed rock masses. However, it is not easy to simulate the rock bolt effects properly by using numerical analysis methods. This is mainly due to the difficulty of modeling jointed rock masses. In modeling the rock masses, there are two approaches available; one is the continuum approach and the other is the discontinuum approach. As far as design works are concerned, the continuum approach is preferable. In this paper, we first pointed out a problem in modeling jointed rock masses, particularly in the continuum mechanics approach. Second, we proposed a basic concept for modeling jointed rock masses reinforced by rock bolts by considering laboratory test results.

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As to the cut-off slope stability the technique of evaluating failure possibility and failure factors of metamorphic rock-slopes has been proposed by the authors using possibility linear system that is based on Fussy set theory. In the present research the technique is applied to existing slopes (different rock types) that fail due to rainfall and the slope-failure factors according to rock characteristics are presented. The relationship between the results of evaluation of slope-failure possibility and slope's service days is derived and the rock characteristics with respect to weathering in progress is presented.

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