Analysis of Factors Influencing Tunnel Block Collapse in Blocky Rock Masses: Insights from Large-Scale Model Experiments and DDA Simulations

Block collapse is one of the most common geological disasters that occurs during the construction of tunnels in blocky rock masses and is characterized by sudden events and severe damage, which seriously threatens the safety of tunnel construction. To achieve effective control of block collapse, model experiments on tunnel block collapses with a scale of 200 × 125 × 23 cm were conducted to study the effect of the tunnel span on disasters in this paper. The height of block collapse increases with increasing tunnel span, which verifies the accuracy of the discontinuous deformation analysis method (DDA) in simulating block collapse by comparing the experimental results with the DDA simulation results. Then, the influencing factors of block collapse disasters were selected, and the effects of different influencing factors on tunnel block collapse were simulated based on the DDA method. According to the simulation results, the height and area of block collapse were obtained, and the influence laws of each factor on the height and area of block collapse were analyzed. Based on that, the impact levels of each factor on block collapses were divided. Finally, based on the K-means method, tunnel block collapses were divided into five levels according to the height and area of the block collapse, accounting for 28.6