Abstract
By Miyagi offing earthquake occurred on May 26, 2003, a landslide-related collapse occurred in a gentle slope of around 10 degrees. This experiment study carried on for make clear the mechanism of collapse at gentle slopes coming about, using a shaking table. The following things became clear from the experiment. By the movement of the sand materials due to vibration, cavities increased, and the pore water pressure rose by repeating decrease, and the result to repeat the decline was provided. As the result of having considered a rise in pore water pressure, the rise type of two patterns was confirmed. As for the first, the volume shrinkage happens by vibration, and the excessive pore water pressure is generated by a cavity decreasing, and a rise of the sudden pore water pressure was recognized. When, as for the second, movement of the groundwater happens by a shake, and the rise of the water table happens. The difference of change for pore water pressure due to earth materials was thought of as distinction of size and water permeance coefficient. Because pore water is hard to move to other cavities by the decrease in cavity generated in the case of the volume shrinkage if a water permeance coefficient is small, the pore water pressure is easy to increase. On the contrary, if a water permeance coefficient is big, groundwater is easy to move, and it is thought that a factor to raise an underground water table becomes. The cause for collapses on a gentle slope was thought to be the rapid change of pore water pressure by seismic movement.
