EXPERIMENTAL STUDY ON COLLAPSE OF COVERED KARST UNDER WATER-LEVEL FLUCTUATION

In order to study the variation of pore water pressure and settlement of karst cave under water-level fluctuation, the laboratory physical model experiment is adopted in this paper. The geological disaster spot of the karst collapse in Longyan City of Fujian Province is taken as the research object. The results show that:(1)The response of pore water pressure is closely related to the fluctuation of the water level. According to the change of pore water pressure, the collapse development of the soil inside karst caves can be roughly determined. (2)The internal collapse of soil caves spread to the upper and horizontal directions simultaneously, but the expansion speed of the upper direction is greater than that of the horizontal direction. (3)The development of subsidence is irregular, and the center of the approximately circular subsidence pit formed in the surface is not on the same vertical line as that of the original cavity. Besides, the collapse model of the covered karst under the cyclic fluctuation of the water level is summarized according to the analysis of the development characteristics of karst caves. At last, the three development stages of the development of the karst cave subsidence are presented:the development of the soil cave, the expansion of the soil cave and the surface collapse. The results of this research can be applied in monitoring and detecting early warning signs of karst cave collapse.