This study investigates the effects of organic matter on lime and cement stabilized Ariake clays with emphasis on their mechanical properties and microstructure. The study also focuses on the effect of humic acid, which is a part of organic matter, on the strength development of stabilized clays. The results show that the strength and the yield stress of lime stabilized clay with high humic acid are low due to the obstruction of the pozzolanic reaction. Consequently, the cementing products are not visible in the micrographs. The humic acid has a greater effect on the strength reduction of lime stabilized clay than that of cement stabilized clay. The effect of humic acid on strength of stabilized clays decreased with increasing salt concentration because the humic acid becomes inactive at higher salt concentration.

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It is found that the difference of consolidated history of an alluvial clay layer may affect the amplification of the vibration of the ground in a reclaimed ground during earthquake. For this reason, soil investigation, laboratory tests and numerical analysis were carried out in order to investigate the mechanism why Rokko Island experienced less liquefaction than the one in Port Island. It is found that the main reason is the existence of a large damping in the reclaimed ground of Rokko Island due to an unconsolidated alluvial clay layer beneath the reclaimed ground.

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A jacket-type steel-pile foundation is a suitable foundation for resisting horizontal forces from earthquake or wind. It can not only reduce drastically the weight of the structure itself by connecting the foundation and the superstructure continuously but also increase the lateral resistance efficiently by using inclined piles properly. In this paper, the dynamic behavior of a group-pile foundation with inclined piles is investigated by conducting dynamic centrifuge model tests. In these tests, the responding acceleration of the superstructure and the loads of the piles during the earthquake are measured carefully. It was found that, in a group-pile foundation with inclined piles, the correlation between the sectional forces and the inertial forces of the superstructure is less than those of vertical piles, indicating that the effects of soil deformation can not be ignored in evaluating the sectional forces, and that there is a possibility that the maximum bending moment of the pile may occur underground if the upper stratum is a soft soil layer.

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Scale model tests and the DEM analysis are carried out to grasp a shear behavior of discontinuous rock masses with rock block of two prominent sets of discontinuities, which are oriented perpendicular to each other.
The results of the model test and the analysis indicate that there is the anisotropy of shear properties between counter-dip arrangement and dip arrangement In the case of counter-dip arrangement, the failure mechanism is dominated by shear failure of intact rock, however, in the case of dip arrangement, it is dominated by tensile failure of intact rock due to toppling failure, which is caused by opening of discontinuities.

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Uniaxial tension tests of Sanjome andesite and Tage tuff were conducted under the four strain rates. A servo-controlled testing machine was used to obtain complete stress-strain curves up to the residual strength region. The results indicate that the Young's modulus increases and the stress-strain curve in the post-failure region shifts to the right-hand side in associate with the increase of strain rate. The results were compared with the creep testing results previously published and the relations between the two were discussed. Finally, uniaxial tension tests in which strain rate was changed between low and high alternatively were attempted and the results were compared with the strain rate dependency.

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Ground surface loading model tests above a tunnel have been carried out to evaluate an analytical method of tunnel lining deformation behavior caused by adjacent constructions such as banks or foundations of structures. Ground conditions of the tests are 2 types; soft mortal and sand.
As a result, nonlinear deformation behaviors of the ground and the tunnel lining were comprehended. And it was shown that these experimental results could be simulated by FEM analysis using a nonlinear ground model and a contact model between ground and tunnel lining.

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A number of plane-strain compression tests are conducted on sand specimens by varying (1) size and shape, (2) end conditions, and (3) strain rate of loading. The deformation patterns of the specimens are investigated based on the viewpoints of three kinds of bifurcation modes: discontinuous shear band mode, lower order harmonic (diffuse) mode, and higher order harmonic (diffuse) mode. As a result, the difference in those conditions has activated different bifurcation modes to entail diversified deformation patterns. The mixed presence of those three kinds of bifurcations is found to create such diversity.

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Segmental lining of flat sectional shield tunnel was discussed through the model experiment. In the experiment, the thickness of the model lining is partially changed to support the momentum, which is remarkably induced at the crown, invert and spring line of the flat sectional tunnel. The knowledge has been obtained that employment of the lining whose thickness is partially varied can reduce the tension strain, and its reason was studied through the calculation based on the conventional designing method of the segmental lining.

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In this paper, a shearing test was carried out under constant normal stiffness condition to understand the mechanical characteristics of discontinuities. By using the result of this test, we propose an efficient methodology to estimate the strength parameters c and φ, in case we assume the strength characteristics of discontinuities follow the Mohr-Coulomb's failure criterion. In addition, we discuss the effect of parameters such as roughness, initial normal stress and normal stiffness on the shearing behavior of discontinuities by comparing the results between the shearing test under constant normal stiffness condition and constant normal stress condition.

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This study focuses on the ground penetration behavior of outriggers due to failure of the ground which causes the overturning of mobile cranes. An experimental analysis and a numerical calculation were performed to investigate the influence of the penetration of the outriggers on the overturning of the mobile cranes. Since mobile cranes become unstable due to rapid penetration of the outriggers caused by brittle failure of the ground, an evaluation of the kinematic instability of mobile cranes is needed for prevention of the overturning. The risks of overturning are assessed based on the sinking characteristics and the pressure acting on the ground.

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In order to understand the combined effect of elevated temperature and confining pressure on fracture toughness, fracture toughness experiments were carried out (1) at elevated temperatures from room temperature to 200°C, (2) at confining pressure from atmospheric pressure to 9MPa using the single edge-notched round bar in bending (SENRBB) specimen of Kimachi sandstone. The experimental results showed that the fracture toughness of Kimachi sandstone did not vary significantly at temperature up to 125°C and increased with elevated temperature beyond 125°C. The fracture toughness of sandstone and tuff was found to be significantly affected by increasing confining pressure.

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Groundwater levels around the water sealed rock cavern are greatly fluctuating by the influence of not only precipitation, air pressure and earth tide, but also changes of water supply for water curtain control. It is very important for maintenance and control of water curtain functions to detect a minor fluctuation caused by changing hydrological structure with earthquake or others in the greatly fluctuated observed values. In this paper, it is shown that the effect of meteorological phenomena can be clearly separated by statistical time series analysis and that the changes of hydrological structure can be detected. It's also shown that the proposed methods are available for the maintenance system.

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The potential of a ground penetrating radar (GPR) for the soil water content and water table determination in a sandy soil were evaluated. It is shown from field experiments that the GPR measurements performed satisfactorily. An artificial sandy soil embankment model was used in a field experiments. The horizontal time domain reflectometry (TDR) probes and observation wells were used to measure soil water content and water table for comparison to the GPR data. A similar trend of water table behavior and values of water contents were measured by TDR, observation wells and GPR methods. GPR system offers a fast and nondestructive way for estimating the soil dielectric constant and may be an interesting tool for low-cost mapping of soil water content and trace the transient behavior of the water table in sandy soils.

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An RTK-GPS is a candidate for a method of monitoring large ground deformation which is caused by liquefaction during an earthquake or by ground sliding. This paper reports application of the RTK-GPS to measure actual ground deformation in an experiment carried out by PARI. The robustness and the accuracy of the RTK-GPS measurement are studied. It is shown that the RTK-GPS does not have serious problems for the robustness, and that the accuracy of measuring the resultant deformation and the dynamic deformation process is satisfactory. These results support the applicability of the RTK-GPS to the real-time monitoring of large ground deformation.

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In water-sealed rock caverns for storing oil, monitoring and evaluating the hydraulic characteristics of the rock mass around the cavern during excavation are very important issues. When the rock caverns were initially constructed at Kuji, Kikuma and Kushikino sites in Japan in 1986 to 1995, however, no systematic rock classifications for such evaluation were available. The records of construction of the caverns at the sites are therefore reviewed to propose “rock classifications based on water sealing function” corresponding to usual rock mass classifications. The standards for evaluating the distribution and continuity of rock fractures, and seepage condition are classified. Grouting, water injection increase and other measures are recommended as patterns according to the results of evaluations including time-based monitoring of seepage condition on the walls of the caverns.

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