Collapse risk assessment of deep-buried tunnel during construction and its application

The hazard of tunnel collapse is a key factor restricting the excavation progress and safety of the tunnels excavated by drilling and blasting. To control this construction risk, a new risk assessment method of tunnel collapse involving case analysis, advanced geological prediction, and Dempster-Shafer (D-S) evidence theory is put forward. At first, after analyzing the typical tunnel collapse cases, 11 influencing factors were adopted as the risk evaluation indices from the natural environment, engineering geological conditions, design and construction, organization and management, as well as advanced geological prediction. Further, the risk indices and their corresponding ratings are calculated to establish the assessment index system. Secondly, for calculating the index weights, the Euclidean distance based on the number of intervals is applied for obtaining the basic probability of each index belonging to each risk grade. Furthermore, the index weights are determined depending on the degree of similarity and support between the indices. Thirdly, the tunnel collapse risk level is obtained based on the D-S fusion rule. In this way, the theory and technical system of risk control of tunnel collapse are established. Finally, the established risk assessment method of tunnel collapse is successfully applied to the Yuxi tunnel. The consequent result is in perfect accordance with the practical condition which suggests that this approach is reliable and practical. This study provides references for other similar tunnel constructions.