Risk Assessment of Karst Tunnel Water Inrush Based on Combined Weighting Method

Sudden water inrush is the primary geological hazard in karst tunnels, which poses significant risks and seriously threatens tunnel construction and safety. To address this issue, this study takes multiple karst tunnels under construction in Guangxi as research objects. Through geological investigation and analysis of the geological conditions and tunnel characteristics in the tunnel areas, this study selects seven key factors affecting tunnel water inrush, including basic quality index of rock mass, rock mass dip angle, rock mass integrity coefficient, surrounding rock saturated uniaxial compressive strength, maximum water inrush of the tunnel, annual rainfall in the tunnel site area during the rainy season, and tunnel burial depth, as evaluation indicators. A combined weighting-TOPSIS method for karst tunnel water inrush risk assessment system is constructed. Hierarchical analysis method is used to establish a judgment matrix to determine the subjective weights of evaluation indicators. Subsequently, the objective weighting entropy method is used to calculate the objective weights, and the combination of the two is used to form a combined weighting method to calculate the combined weights. Finally, based on the combined weighting-TOPSIS method, the distance and relative closeness between the cross-sections of karst tunnels under construction and the ideal solution are obtained to evaluate the risk of water inrush in karst tunnels under construction. The evaluation results have been well validated in advance geological drilling, demonstrating the feasibility of this method for literature evaluation of karst tunnel water inrush.