Large-scale cyclic-loading pushover test method and its verification for seismic damage of underground structures

It is difficult to effectively simulate the seismic damage characteristics of underground structures and their failure process in the current shaking table model tests. A large-scale 1∶7 pushover test on an underground subway station structure is designed and carried out. Taking Daikai subway station structure as the prototype, considering the equivalent soil pressure and the interlayer displacement ratio division system, the cyclic-loading curve based on displacement is finally determined. At the same time, it is compared with the results of the numerical simulation. The results show that the tensile cracks appear at the ends of the column earlier than at the other components of the structure, and then the compression damage occurs. As the bearing capacity of the column decreases, the internal forces of the structure begin to redistribute, and the overlying soil pressure gradually transfers to the walls, which causes the cracks at the ends of the roof to start to develop. At the same time, the concrete at the ends of the walls is damaged, and finally, the structure eventually loses its bearing capacity. Compared with the numerical simulation results, the designed large-scale pushover tests on the seismic response of the underground structures can accurately simulate the seismic failure process of the single-story underground station structures. At the same time, compared with the existing researches on the seismic performance levels of the single-story underground subway station structures, it is further verified that the proposed new large-scale pushover test method can reasonably reproduce the seismic performance levels of the single-story underground structures.