Yaichi MIMURA

Unsaturated shear properties of sand obtained from tunnel construction site of Tohoku Shinkansen

Hirofumi TOYOTA

The earth disasters have been caused by local heavy rainfall, and the infrastructures such as cut slopes and embankments have been damaged in our country. Moreover, a tunnel was collapsed during excavation in a tunnel construction site of Tohoku Shinkansen. It is considered that the rise of the groundwater level caused this collapse. Therefore, it is important to prevent such ground disaster. Triaxial compression tests were conducted by using saturated and unsaturated sands extracted from Sanbongihara tunnel of Tohoku Shinkansen (Hachinohe and Shin-aomori route) to examine the stability of cutting face in the research. Three kinds of specimens with different densities were prepared for the experiments. The shear characteristics were investigated using the specimens applied different matric suction.
The results obtained in this research are follows:
1.In stress-strain relationships, the more obvious peaks appeared in the case of larger density and larger matric suction, and the strengths showed the softening behaviour.
2.In volumetric strain, larger dilatancy appeared in the case of larger density and larger matric suction.
3.The internal friction angle increased with density and the cohesion increased with matric suction.