This study proposes a method for designing the bottom slabs of composite caisson breakwaters considering the unevenness of rubble mound surfaces. Based on the results of large-scale model tests, we developed a stochastic model to represent the distributions of reactions acting on the bottom slabs of caissons. We then conducted reliability analyses on the model to calculate the bending failure probabilities of the bottom slabs with respect to the mound unevenness. We also evaluated the partial factors to be used in designing the bottom slabs of caissons at various degrees of mound unevenness.

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In in-situ compaction method, where the material is directly compacted in the disposal pit, possible damage to the surrounding rock and waste package due to the impact of compaction are issues of concern. While an evaluation of the effect of impact is necessary, the analysis based on Finite Elemental Method (FEM) has not yet been achieved with sufficient accuracy. Experiments were carried out and data obtained for the acceleration damping characteristics of the buffer material. The results were then used with an analytical model in order to improve the accuracy of the analysis. By comparing this with data obtained from full-scale experiment, it was possible to confirm the validity of the analysis that takes acceleration damping characteristics.

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The Niigata-ken-Chuetsu earthquake of October 23, 2004 caused widespread liquefaction in the alluvial plain of the Shinano River and southwestern coastal lowlands facing the Sea of Japan in Niigata Prefecture. We conducted reconnaissance investigations immediately following the earthquake, focusing on soil liquefaction and associated damage to structures. In addition to the field reconnaissance, we interpreted aerial photographs taken after the earthquake to determine the spatial extent of liquefaction. Sand boiling was more frequent and severe in Yoita, Mitsuke, Nagaoka and Ojiya in the northern region of the epicenter bordering the Shinano River, and Kashiwazaki and Kariwa in southwestern coastal lowlands. The liquefied soils classified into four types: fluvial sand deposits of the Shinano River and its tributaries, backfill on gravelly deposits, fill and/or backfill on soft cohesive or organic soil deposits, and natural dune sand on lower slope of coastal dune.

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There are several types of failure patterns such as those proposed by Terzaghi, Meyerhof and Vesic. But those have been proposed for the purpose of design calculation and are not based on close obsevation of real behavior. The objective of this paper is to visualize and to characterize the failure patterns of the ground under vertically loaded pile foundation using X-ray CT scanner. Here, a series of model loading tests with different conditions such as shape of pile tip, effect of loading process, soil density and loading speed were conducted and the model ground was scanned in each case. Finally, the bearing capacity mechanism due to vertically loaded pile was visualized and evaluated in three dimensions without any destruction for the first time and it is convinced that X-ray CT is one of powerful tool in geotechnical engineering.

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The pressure-plate and the gravity drainage column experiments were conducted to confirm the efficiency of the empirical equations explaining the Water-NAPL-Air three-phase capillary pressure-saturation relationships. The pressure-plate experiments showed that water saturation is identical to the water retention characteristics under air-water two-phase condition. On the other hands, the gravity drainage column experiments showed that total liquid saturation distribution under three-phase condition was not agreed with the oil retention characteristics under air-oil two-phase condition, when oil thickness was thin.

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Consideration of the deterioration of rock due to chemical attack from such things as fossil ground water or salts of seawater origin and a change in environment due to air supply is important for high-level nuclear waste disposal. The quantitative evaluation of the chemical attack is important but current experimental methods are too vague. This is especially so for slaking test, where such chemical conditions are not considered and the analysis of the immersion solution that may cause rock deterioration is not prescribed, either. Therefore a new valuation method has been proposed incorporating a laboratory slaking test taking into account of the chemistry of water quality and air supply conditions and simulating chemical conditions for sedimentary rocks.

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In the current design and practice of earthquake geotechnical engineering, the liquefaction potential of soil layers under groundwater levels is evaluated based on laboratory tests on fully saturated soils. However, it is known that partly saturated soil layers exist below groundwater tables.
In this study, in order to properly evaluate the liquefaction potential of such partly saturated soil layers, the field tests and laboratory triaxial tests were conducted. Based on the relation between B-value and elastic wave velocities from these both tests, liquefaction potential at 4 sites, damaged by the past earthquakes were evaluated. As the results, by taking into account of in-situ saturation condition, it is found that it is possible to evaluate liquefaction potential equivalent to actual liquefied situation.

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In order to investigate the deformation and strength anisotropy of compacted decomposed granite soils, a series of unsaturated and saturated-drained triaxial compression tests were performed. The sample had three different angles of the axial direction to horizontal plane δ=0, 45 and 90 degrees. The compression strain of specimens subjected to an isotropic compression was influenced strongly by δ. And the effect of the δ on the strength was clearer in the unsaturated specimen than in the saturated specimen. Moreover, we propose a new procedure, which can be applied in the shear strength τ of the unsaturated specimen in consideration of the δ.

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The bearing capacity characteristics of compacted soft rock materials are examined based upon the results of some laboratory tests such as a slaking and a crushing tests and CBR test, etc. As a result, it is revealed that the relationship between CBR and air-porosity of a specimen is unique and specifies the critical air-porosity, and the bearing capacity of a specimen is mostly affected by the material properties and the degree of repetition of dry - wet conditions. Moreover, it is shown that the characteristics of critical air-porosity have close contacts with the material properties.

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It has been shown experimentally and theoretically that a soilbag which is merely wrapped with a thin bag has unexpectedly high compressive strength, and it can be used as the reinforcement material of building foundation and retaining wall. The piles of soilbags have a unique property of vibration reduction due to their flexibility and individuality (the assembly of discrete soilbags). Based on such a unique property, three methods of vibration reduction are introduced at the place of vibration source (under the traffic road), on the propagation path and at the place of vibration reception (under the building foundation), and are checked by the vibration measurements (vibration level,vibration acceleration and its frequency analysis). In particular, the piles of soilbags can reduce the vibration below 10 Hz (sensitive vibration for human body) effectively, which is difficult to reduce in a usual way.

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This paper shows development and application potential of H-jointed steel pipe sheet piles (SPSPs) with H-H joints on vertical cuttoff barriers used in coastal landfills. The authors have developed a number of technologies such as developing the H-jointed SPSPs and H-H joints for SPSP joint sections aimed at improving performance and widening application areas of SPSPs. Hydraulic conductivity of the H-jointed SPSPs with H-H joints was evaluated by experimental studies. As a result, hydraulic conductivity of 10^-8 cm/s is proposed for use in design of H-jointed SPSPs with H-H joints sealed with this water-swelling hydraulic sealant sheet in applying as a hydraulic cutoff wall in coastal landfills.

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When the ballast track on a soft roadbed is replaced with a ballastless track which has high rigidity, outflow of roadbed soil or even roadbed caving may occur. Since the growing process of roadbed degradation under a ballastless track has not been clarified, reasonable countermeasures have not been developed yet.
In this study, we discussed the growing process of the degradation of cohesive-soil roadbed under a ballastless track by performing moving wheel loading tests to simulate actual trainloads. As a result, we confirmed that the roadbed degradation under a ballastless track was caused by the piping-outflow of the surface soil whose effective confinig stress was not increased enough by the dynamic porepressure due to train loads. Thus, we were able to clarify the basic policy on the countermeasures against such degradation.

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In order to design the foundations of large scale structure, first we cleared mechanical properties on layered sedimentary soft rocks based on laboratory and in-situ tests. Then we showed that results of in-situ tests can be simulated by using properties obtained from laboratory tests. Next we analyzed the main factor of scale effect between the loading plate size of in-situ tests and real structure size. As a result of numerical analysis considering this main factor, deformation modulus was larger as the loading plate size was larger and scale effect concerned with shear strength properties did not appear in the scope of this examination. According to these examination, we verified rational and reliable properties on layered sedimentary soft rocks for the foundations of large scale structure.

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Acidification with pyrites changes geotechnical properties of cohesive soil extremely, and will cause geotechnical disasters such as slope failure etc.. In order to clarify the influence of the acidification on geotechnical properties, the cohesive soil with pyrites is investigated with a series of laboratory tests. The following conclusions are obtained from the present study: 1. Acidification of cohesive soil with pyrites reduces liquid limit and plastic limit. 2.Unconfined compressive strength decreases gradually by acidification of cohesive soil. 3.Sulfate content of cohesive soil influences consistency limit and unconfined compressive strength.

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From the experience with many tunnel projects in rocks it is suggested that the ground arch effect in rock can be obtained by controlling a loosening zone. The loosening is considered as the post-peak behavior of rocks. The authors investigated the motorway tunnel which was driven through the tertiary sedimentary rocks in the northern Osaka, and confirmed as follows: Such a small change as 0.1 MPa in the confining pressure, which acts onto the tunnel wall as the resultant effect of support elements, remarkably influences the extent of loosening zone. A magnitude of loosening zone can be quantified through the rock classification and the strain-softening model proposed by Tanimoto et al.

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It is well known that the behavior of discontinuous rock masses is strongly influenced by the properties of discontinuities distributed in rock masses. Those are the conditions of geometrical distribution and mechanical properties of discontinuities. This paper deals with the mechanical properties of discontinuities. The mechanical properties of them, basically, should be obtained by laboratory and/or in-situ shear tests, and then those properties can be determined. However, the test results vary from the size of specimens used, what is called scale effect. The persistence of discontinuities in the real rock masses is from tens centimeter to tens meter. Since, in order to estimate the actual behavior of rock masses using test results, it is required to consider the influence of scale effect. This paper describes the comprehensive review about the researches up to now concerning the scale effect of discontinuities and suggests the practical determination method of shear stiffness, shear strength, dilation and normal stiffness to be used for the analysis of rock masses behavior.

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In this study, triaxial compression test under low confining pressure and undrained state were carried out for saturated and unsaturated kaoline specimens and undisturbed sample, to study the effect of suction reduction caused by wetting process, and effective stress path shear and strength characteristics were examined. From the test results, it was found that the intergranular adhesive force between soil particles affects on the peak strength, and that the residual strengths were arranged uniquely for the effective mean stress taking the suction stress as confining pressure. And we proposed one prediction method for the strength reduction caused by decrease of suction during wetting process.

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The coefficient of air permeability and the influence radius are the important indices for the design of remediation of the polluted unsaturated soil. At present, several theoretical formulas have been proposed to estimate the air permeability. However, neither theoretical formulas for estimating air permeability nor the influence radius of vacuum test affected by the volumetric water content are clarified.
In the present paper, the solutions by theoretical formulas were compared with numerical solution by the finite element method which considers the compressibility of air and the spatial distribution of volumetric water content. It was revealed that the theoretical formulas were applicable to the actual unsaturated soil where the in situ vacuum test was conducted.

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The multi-layer soil improvement method which permitting partial softening and liquefaction of the ground involves placing multiple plate-like layers of improved soil in a liquefiable layer was proposed. In this study, different soil improvement methods including the proposed method were tested using shaking tables while the percentage of layers of improved soil in the ground was varied. The effectiveness for attenuating seismic ground motions and for controlling settlement was examined to assess soil improvement effects of different methods. As a result, it was found that the multi-layer soil improvement was effective for attenuating seismic motions and repression of settlement.

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This study conducted out unconfined compression test and constant stress direct shear test for an unsaturated non-plastic silty soil with high soil suction. High soil suction was applied to all of soil specimens using vapor pressure technique. The cohesion obtained from unconfined compression tests increased with the soil suction. The constant stress direct shear test data sets, however, described that the cohesion remained constant in widely high soil suction ranges. The cohesion obtained from direct shear test was larger than that obtained from unconfined compression test. It was clear that the difference of shear process affected relationship between cohesion and suction in high soil suction ranges.

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This research is to clarify the mechanism of the loosing phenomenon of the surrounding ground as a long-term influence by the excavation of the close parallel shield tunnels. The research examined the effect of loosing quantity by the occurrence of tail-void and the effect of distance of the parallel tunnels. The model experiment was conducted, in which aluminum rod mass using two tunnel models was applied as a simulated ground, and the simulation analysis by distinct element method (DEM) analysis was done. As a result, the soil pressure that was on the first tunnel increased by the influence of excavation of the second tunnel, and the ground arching effect which strides over two tunnels was confirmed. Moreover, the results of analysis and experiment were also compared with measuring results in the construction.

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Mudflow type failures of natural slope and artificial fill composed of volcanic sandy soil occurred during past earthquakes. In this study, the results of cyclic tri-axial tests of unsaturated volcanic sandy soil measuring pore air pressure, pore water pressure and volume change of soil are reported. Tests are conducted for specimens with various initial suctions and the same dry density under undrained condition both for pore air and pore water. Loose volcanic sandy soil specimen subjected to cyclic shear lost effective stress even if the degree of saturation was about 75%. Based on the test results, the liquefaction mechanism of unsaturated soil was discussed. It was concluded that the fluidization potential depended on the degree of saturation (initial water retention condition) and volume compressibility of the soil.

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This study researched the effect of montmorillonite content on the thixotropy of compacted soils. We conducted fall cone tests and unconfined compression tests on sample soils, each one of which contained a different amount of montmorillonite.
As a result, the compacted soil with a much lower content of water than the plastic limit, mixed with bentonite and kaolin, increased the thixotropy strength. The tests also showed that the strength varies depending not only on the ratio of montmorillonite content but also on the period of elapsed days and the temperature. Furthermore, the tests showed that the axial strain at failure and the modulus of deformation as well as the strength of the unconfined compression all vary depending on the period of elapsed days. Thus, it was determined that the strength of thixotropy can be evaluated in soil construction by compaction such as embankment.

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