Risk Evaluation System for the Impacts of a Concealed Karst Cave on Tunnel Construction
(1 Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092;2 Department of Geotechnical Engineering College of Civil Engineering Tongji University, Shanghai 200092; 3 CCCC Rail Transit Consultants Co. Ltd., Wuhan 430056; 4 Anhui Comprehensive Transportation Research Institute Co. Ltd., Hefei 230000)
Abstract：
Concealed karst caves, a major hidden danger in the construction of tunnels in karst regions, are in? clined to cause serious accidents such as water bursts and mud gushing, collapse and subsidence. Few systematic studies have been carried out concerning karst cave related risk identification and warning theories. Based on case statistics and theoretical analysis, geotechnical and construction risk factors were selected for studied. The geotechnical factors include the orientation of a karst cave relative to a tunnel, the type and filling condition of the karst cave, the interval between the cave and the tunnel, the grades of the surrounding rocks and the karst cave scale. The construction factors include advanced geological forecast and construction monitoring. Considering the relationship between risk factors and construction accidents regarding karst tunnels, the constant weights of various risk factors were calculated using the Analytical Hierarchy Process (AHP). In light of different karst tunnels, the weights of risk factors were calculated by variable weight theory based on constant weight. Considering the evolution rules of karst tunnel safety accidents, the valuing scope of risk factors was determined, and grading standards for the risk evaluation of concealed karst caves were presented. The feasibility and rationality of the evaluation system were verified through practical cases.
2017, Vol. 54 