Large-scale model experiment of ground collapse induced by water and sand gushing in subway tunnels

To study the mechanism of ground collapse induced by water and sand gushing in subway tunnels, a large-scale model test system which may simulate the action of water seepage in tunnel is developed. With Qingdao Huangdao station with the water and sand gushing taken as an example, the evolution process of ground collapse induced by water and sand gushing in this subway tunnel is reproduced, and the corresponding mechanism of ground collapse is further revealed. The research results indicate that there is a close correlation and hysteresis between ground deformation and sand inflow. In the early stage of water and sand gushing, the ground surface deformation increases slowly, the soil pressure and seepage pressure of clay are basically unchanged, and the seepage pressure near water gushing point increases gradually. In the middle stage of water and sand inrush, the soil pressure and ground surface deformation increase sharply, while the seepage pressure near water inrush point decreases steeply, while the seepage pressure of clay increases rapidly, which not only provides evident precursor information of soil collapse but also reflects the instantaneous characteristics of soil collapse. In the later stage of water and sand gushing, the ground surface deformation, soil pressure and seepage pressure near water gushing point remain relatively stable. During the process of water and sand gushing, the variation law of deep soil displacement is similar to that of ground deformation. The results of the model test for ground collapse induced by water and sand inflow may provide guidance for the prevention and control of similar projects. © 2023 Editorial Office of China Civil Engineering Journal. All rights reserved.