Abstract
Pore air has a significant influence on the seepage and stress in an unsaturated ground. The aim of this study was to obtain the local collapse of the ground due to the increase in pore air pressure when pore air was entrapped in the ground following a rapid increase in the water level and the saturation of the surface ground. One-dimensional seepage tests were carried out, measuring the pore air pressure, the amount of charged water, and the displacement at the surface of the specimen. The experiments proved that the soil specimen had collapsed over the critical pore air pressure, which rose in proportion to the amount of infiltrated water. In addition, the rate of the collapse development was found to correlate linearly to that of the inflow water. The ground was threatened by collapse due to the ascent of air pressure when the surface ground was saturated or there was low permeability of the air. Rapid infiltration to the zones of accumulated air, such as subsurface cavities or pipes, induced the increase in air pressure.
