Trapdoor model tests using a soil box with multiple movable base plates were conducted to study the earth pressure distribution associated with differential settlement of subsoil. Spherical glass beads were tested to assess fundamentals of arching mechanism. Discrete element method simulations were performed considering equivalent particle size and material properties. It was found that the earth pressure distribution varies with varying burial depth, and arch formation is observed with increasing the depth. Arching action is further confirmed by evaluating the shear pressure distribution and the ground surface settlement. These observations are in good agreement between experiments and simulations.
The elastic wave velocity is essential to estimate the stiffness of geomaterials. In this study, disk-shaped piezo-ceramic transducers are used to determine shear wave and compression wave velocities at various stress states. Silica sand specimens confined at an isotropic stress of 100 kPa were sheared monotonically at a low strain rate while keeping the cell pressure constant, and wave measurements were performed at various strain levels simultaneously during the shearing process. The wave velocities are sensitive to both the void ratio and stress states; however, they tend to converge to a critical value at a large axial strain.
The Kumamoto earthquake sequence that started from Mj6.5 earthquake on April 15, 2016, caused serious damage to various structures including lifeline facilities. Akita water source area and Numayamazu water source area, which located near the Kiyama River basin of Higashi-ku, Kumamoto City, were damaged. In this area, many pump towers tilted and function stopped. Also we found ground subsidence. In this study, we try to evaluate of the surface ground behavior during the earthquake by numerical analysis approach. Strong ground motion during the main-shock which recorded in borehole at near source area was used as input motion. We focused on acceleration and shear strain distribution in the surface ground.
In order to investigate the slaking induced creep deformation and shear strength reduction of crushed mudstones （JGS slaking index = 1）, a series of direct shear tests were conducted under the different stress ratio and initial water content of the specimen. The specimens at different initial water content were subjected to full-saturation under creep shear stress condition. After when the creep shear displacement became stable, a monotonic shear loading was applied. It was found that the creep shear deformation by immersion became larger as decrease in the initial water content and increase in the stress ratio. The shear strength tended to decrease as shear deformation by the immersion became larger.
This study aimed to investigate the pore structure of middle scale column specimens exposed outdoors. The results revealed that pore structure of the part where the influence of rain is small was coarse compared with the part where the influence of the rain is large. As the results of analyzing the pore structure at the age of 28 days and 7 years and 8 months, it was confirmed that the pore structure was coarsened as much as the surface part regardless of the curing method and the difference of water cement ratio about 5%.