ABSTRACT

Sinkholes or cave-in’s of the ground often occur in urban roads. The complicated underground situation as well as the necessity of urgent restoration do not usually allow full investigation of the real cause. The detailed mechanism of the phenomenon has not been, therefore, well understood. A cave-in is usually initiated by the formation of a cavity in the ground. It is possible that the hidden cavity expands to eventually cause apparently sudden collapse. In this study, a series of model tests simulating the process of subsurface cavity formation/expansion was conducted, using a small soil chamber having an opening in a base plate. A cavity was formed above the opening at the base, after the water with soil flow out. It was found that a cavity and loosened ground above the cavity can extend rapidly upward when the ground consists of poorly graded sand, especially when it is fully saturated.