Dewatering induced karst collapse conditions and safety prevention and control measures in Nanning subway construction

Extracting groundwater is an important factor triggering karst collapse. However, there are few studies on critical parameters and safety prevention and control measures for karst collapse induced by extracting groundwater. Taking the East Metro Station of Sports Center No. 4 of Nanning subway as an example, this paper analyzes the conditions of karst collapse induced by dewatering during the construction. According to the disintegration test and the pipeline flow test, the critical condition parameters of karst collapse development of unsaturated soil and saturated soil are obtained. Three safety measures are proposed to effectively prevent karst collapse, such as the surface water blocking, controlling soil water content higher than 14.65%, and controlling pumping rate less than 4.4 m3·d-1.