Abstract
It is very severe circumstance for underground public works structures such as subway tunnels that the surrounding soil is greatly distorted during an earthquake. This paper adds new knowledge to the previous paper which studied that what kind of base input-earthquake-motion waveform cause large shear strains in the subsurface ground.
In this paper, a single-cycle-rectangular-shape wave is taken up as base input acceleration motion which forms a single-triangular-shape wave in the velocity of the base movement, and the shear strain induced in the subsurface is analytically studied. Then the mechanism of the subsurface strain generation by this excitation condition is elucidated, and it is pointed out that the amplitude and the rise time of the base motion velocity govern the magnitude of the shear strains. It is strongly presumed that the microscopic mechanism of shear strain generation that has been studied about the elementary wave is revealed in response of the subsurface to a real base excitation with a random waveform.
