?In this study, an immersion test using high concentration of magnesium chloride solution was carried out to develop an accelerated deterioration testing method. This test will help to investigate the deterioration rate and the mechanical properties of deteriorated cement stabilized soil quickly. In addition, unconfined compression tests were performed on the deteriorated stabilized soil specimens under magnesium chloride solution and normal concentration of artificial seawater to examine the difference in strength characteristics, respectively. As a result, it was confirmed that the evaluation method of the deterioration rate shown in the previous studies can be applied even when high magnesium chloride solution is used. It was shown that the promotion method using high concentration of magnesium chloride solution matches the reduction rate of unconfined compressive strength and deformation modulus within the range of 6% and 2% respectively, as compared with the case of using artificial seawater.
?In this report the grid-form deep mixing wall was discussed as the liquefaction countermeasure method for existing structure. If the grid spacing is wider due to the existing structure, the effect of liquefaction countermeasures will be reduced. Therefore, in this study, liquefaction countermeasures by combining oblique wall with relatively wide-interval grid-form deep mixing wall improvement was investigated. It was found that liquefaction can be suppressed if measures are taken in combination with oblique wall of about 1/3 of the depth of grid-form deep mixing wall. It was also found that when the grid-form deep mixing wall and the oblique wall are not rigidly connected, the subsidence after liquefaction will be larger than that that is rigidly connected. However it will be about half that of no countermeasures. According to static numerical analysis, the horizontal rigidity of the grid-form deep mixing wall combined with the oblique wall is about 5 times larger than that of the grid-form deep mixing wall alone. Therefore, it is considered that the liquefaction was suppressed.
?To investigate deterioration rate of rocks, the authors conducted measurements of physical properties of naturally weathered Kimachi sandstone and forcedly deteriorated Kimachi sandstone. The naturally weathered Kimachi sandstone was obtained by boring from an excavation surface where it passed about 100 years since the last digging. From the measurement results of physical properties of the naturally weathered Kimachi sandstone, the relationships between the properties and depth or time were obtained. And the forced deterioration experiments were carried out by the repetitions of drying-wetting and drying-wetting-freezing-thawing. As the experiment results, it was revealed that the ultrasonic wave speed decreases with the cycle of the curve approximated well with logarithmic function. The deterioration rate of Kimachi sandstone was shown by applying values of naturally weathered Kimachi sandstone to an approximate expression obtained from experiments.
?The goal of this study is to assess the stress-strain characteristics of rocks that exhibit Class II characteristics. First, after considering the grain of a stone, the constant stress rate method was applied to perform a uniaxial compression test utilizing Inada granite with three different loading directions. The stress-strain curve was measured up to the peak stress, and the microscopic fracture mechanism was studied. Second, the loading direction was set to three types, and the complete stress-strain curve, including after the peak stress, was evaluated using the stress feedback method, and the anisotropy of the complete stress-strain curve was examined. The mechanical model that explains the fracture under uniaxial compressive stress has also been improved. Connecting the parallel spring models in series equivalent to four stages was found to explain the fracture behavior of granite relatively well. In addition, the outcomes of discussions on microscopic and macroscopic destruction of Inada granite were reported.
?As a case of a slope with increased load of ground anchors, applicability of 2D elasto-plastic finite model was examined for load prediction of ground anchors after cutting. In the finite element analysis, we determined the ground parameters that can reproduce the measured increase in load by an inverse analysis. Next, as a predictive analysis, the load of the anchors after cutting was obtained using the model calibrated by the inverse analysis. As a result, the load of the ground anchors after cutting by FEM analysis showed values in the range of -4.0 to 9.2% with respect to the measured values. This result suggests that the FEM model calibrated by the inverse analysis using the load measurement values of the anchors may be used for rough prediction of load after cutting.