Abstract: This case study presents the collapse that occurred on April 6, 1999, at Zhonghua North Road in Guiyang. The paper systematically demonstrates the entire process of physical modeling experiments on collapse of an underlying karst rock cavern, which includes generalization of geological models, selection of experimental variables, design of similarity ratios, design of physical models, design of similar materials, and physical model testing. A total of 15 sets of physical model experiments were formulated and implemented. The core objective of these experiments was to explore whether there is a positive correlation among three influencing factors the dimensions of soil cavities, the amplitude of water level drawdown, the rate of water level drop and the susceptibility to collapse of underlying karst rock caverns. The experimental results indicate the following: 1）The collapse of underlying karst rock caverns is influenced not only by the gravity and the negative pressure but also by the effect of underground erosion. 2）Throughout the collapse process, the settlement of surface soil continues to develop. In the early stages, the subsidence of surface soil is small but steadily increases. In the later stages, the subsidence rate continues to increase, ultimately leading to “sudden”, “instantaneous” collapse. 3）There is indeed a positive correlation between the size of karst rock cavities, the amplitude of water level drawdown, the rate of water level drop, and susceptibility to collapse of underlying karst rock caverns. Specifically, the larger the radius of the soil cavities, the more likely it is to collapse; the larger the water level drawdown, the more likely it is to collapse; and the larger rate of water level drawdown, the more likely it is to collapse.

Key words: Karst Rock Cavern Collapse, Soil Cavity Dimensions, Amplitude Water Level Drawdown, Rate of Water Level Drop, Physical Model Testing