Three-Mechanism Theory (TMT) of karst ground collapse and its application

In order to provide theoretical basis for the prediction，monitoring，prevention and emergency response of karst ground collapse，the development law of karst ground collapse is summarized. It is considered that the soil body，karst and inducing factors are the three elements leading to karst ground collapse. Karst provides passage and storage space for the failed soil body. The geotechnical properties of soil determine the ways of soil collapse："clay block" collapse，sand particle leakage and soft soil loss. According to the mode of soil collapse，the Three-Mechanism Theory of（TMT）of karst ground collapse，which is composed of "soil cave type collapse"，"hourglass type collapse" and "mud flow type collapse"，is put forward here. In cohesive soil and dense sandy soil layers，under the action of the external force，the ground collapse caused by the failure of soil cave roof is called soil cave collapse. The ground collapse caused by the leakage of sand particles in the loose sand layer above the soluble rock is called hourglass collapse. The surface collapse caused by the loss of soft soil above the soluble rock to the soluble rock under the action of external force is called mudflow collapse. The TMT focuses on the way of soil collapse，which not only explains the phenomenon of karst ground collapse，but also answers the question of "how to collapse". The inducing factors are the external influencing factors of ground subsidence，not the constituent elements of collapse mechanism. Inducing factors produce acting force，which changes the movement state of soil particles，making the soil particles from “static” to “moving”，and the soil mass from “stability” to “collapse”. According to the TMT，a comprehensive geological prediction method of karst ground collapse is proposed，and a deterministic prediction model of soil collapse based on three collapse mechanisms is established. The monitoring，prevention and emergency measures of karst ground collapse are systematically summarized，and a complete karst ground collapse ideological system from theory to practice is formed.