Abstract:Based on the local site bedrock earthquake acceleration time history for different exceedance probabilities of 63%, 10%, and 2% in 100 a given by The Report of Seismic Safety Evaluation for the First Project of Lanzhou City Rail Transit Line 1, the finite difference method was used to analyze the seismic response of the tunnel cavern. By applying bedrock seismic ground motion to the base of the model and by setting monitoring points to observe the lining structure's bending moment, axial force, and shear force, the tunnel structure's seismic response under working conditions at probabilities of exceedance of 63%, 10% and 2% was obtained. The results show that the maximum bending moment of the tunnel lining structure is located in the tunnel vault, the maximum axial forces are located in both the tunnel vault and at the bottom of the tunnel, and the maximum shear force is located in the upper or lower tunnel sidewalls. Tunnel structure's internal forces were found to increase as the excess probability decreased. Using the structure's internal forces at the probability of exceedance of 63% as a point of reference, when the excess probabilities were 10% and 2%, the maximum bending moment increased 1.2 and 1.7 times, respectively, the maximum axial force increased 1.3 and 1.5 times, respectively, maximum shear force increased 1.5 and 2.9 times, respectively. This indicates that the tunnel structure could experience shear failure with strong seismic ground motion.
