Triggering factors and prevention-control countermeasures of karst collapses caused by tunnel construction in the Zhongliangshan area, Chongqing

The Zhongliangshan area is a natural barrier of the east-west traffic channel in Chongqing, that seriously hinders urban economic development. The tunnel traffic can quickly cross fold mountain areas. However, tunnel construction often induces serious karst collapse, failure of underground aquifers and surface water drainage, threatening tunnel safety construction and making impact on the ecological and geological environment. The main controlling factors of karst collapse are variable in different stages of tunnel construction with water level drainage. Therefore, the process of karst collapse can be divided into two stages: sudden drawdown and drainage. The main controlling factor of karst collapse is vacuum suction effect and the sudden change of water and gas pressure in the cracks of karst pipelines, respectively. Furthermore, the prevention and control measures of karst collapse are put forward in this paper. It provides a solid geological basis for effective management of geologic hazard by local karst collapse.