Mechanism of shock absorption layer and shaking table tests on shaking absorption technology of tunnel across fault

Based on the wave function expansion method, the dynamic response analysis of a deep buried cylindrical composite-lining cavity with a new buffer layer mode, namely "rock- buffer layer-primary support-secondary lining" mode, in an elastic space subjected to incident plane SV waves is made. The factors affecting the dynamic stress concentration of the lining structure, elastic modulus and thickness of the buffer layer are discussed. By conducting the large-scale shaking table model tests on the tunnel across the fault zone, some engineering significant conclusions are drawn by analyzing the dynamic properties and fracture patterns of the tunnel across the fault and that with buffer layer. With the lower elastic modulus and smaller thickness of the buffer layer, the dynamic stress concentration of the secondary lining decreases, but the best ratio of the elastic modulus of the buffer layer to that of the surrounding rock is between 1/10~1/20, and the optimal thickness of the buffer layer is no larger than 0.2 m. With the buffer layer, the lining peak acceleration and the dynamic strain amplitudes of the lining decrease. Most of the complex and wider cracks of the lining concentrate on the spandrel and arch foot when the tunnel crosses the fault zone, however, the number of lining cracks decreases with shock sorption joint layers, which shows that the force status of the lining is significantly improved. Wider cracks occur on the ground surface along the fault, and many smaller cracks intersect the fault, which shows that the tunnels and surrounding rock are damaged by shearing force when it crosses the fault, and the number of the crack on the top surface is reduced with the buffer layer. The research conclusions may provide references for the shock and sorption design of tunnels across fault, and they are of important practical engineering significance.