Experimental Investigation of Catastrophic Cover-collapse Sinkhole Formation

Cover-collapse sinkholes develop abruptly and can lead catastrophic damages. In order to study the mechanism of cover-collapse sinkhole formation, we set up a two dimensional experimental model and analyze the critical conditions of soil cavity expansion and collapse and discuss the role of the seepage force in the formation of sinkhole. A forecasting model of sinkhole collapse coupled the mechanics and flow is established in which a critical dimensionless number was used to evaluate the sinkhole development. The results show that: The impact of hydrologic conditions on the cave expanding is generally dramatic and geology (the scale of the opening, soil property, thickness of soil layer, etc.) plays a critical role in sinkhole development. The weak opening of the limestone by karst processes under the clay layer is the essential condition which can cause an arch in clay immediately; due to downward seepage force, the arch develops into soil cave which would expand upward stage by stage as a result of failure of soil. A short false stability exists between two contiguous stages until the arch of the soil cave cannot support the soil roof and then the sinkhole collapses. Moreover during the process the cohesive force of the soil is the major resisting force of sinkhole development.