Analysis on formation mechanism and process of karst collapse in Xiamao Village, Guangzhou City of Guangdong Province

Karst ground collapse in the study area are serious, the geological environment conditions are extremely complicated, the thickness of the Quaternary cover soil layer is large, the silty clay layer is developed at the bottom, and the hidden bedrock is the Hutian group limestone, caves and fault fracture zones are developed. The size of a single cave is usually very large, and the connectivity between the caves are good. The karst ground subsidence occurred with the disturbance of the silty clay layer or the sand soil layer and the formation of the soil hole. According to the characteristics of the double layer structure of the overlying layer in the studying area, the ground subsidence and the development of the soil hole could be divided into the sub-structure collapse mode of "under-adhesive sand" and the multi-structure collapse mode of "under-adhesive sand and soft soil". The collapse mechanism of karst collapse in subsidence area is mainly mechanical penetration, and the collapse development has experienced four stages. It is suggested that underground construction activities and pumping and arranging groundwater in a certain area in the exploration area is inappropriate. So as to avoid changes in groundwater dynamic conditions and reoccurrence of karst ground collapse.