Seismic response of utility tunnel in horizontal nonhomogeneous site based on improved discrete element method

During the construction of the utility tunnel, it is inevitable to cross a horizontal nonhomogeneous site, which adversely affects the seismic resistance of the utility tunnel. This study investigates the dynamic response and damage mechanism of both the utility tunnel and surrounding soil under seismic action through shaking table tests and improved discrete element numerical methods. Firstly, a scaled model of the utility tunnel was constructed and subjected to shaking table tests. Then, an energy-based differential quadrature method (DQM) and Newmark-beta method were derived and applied to the discrete element to construct the tunnel numerical model. The vertical displacement, increment in earth pressure, relative slippage between the tunnel and soil, as well as strain within the tunnel were analyzed in detail, and the response mechanism of the tunnel and the surrounding soil was revealed by using the improved discrete element method. It was observed that the sidewall earth pressure increment follows an approximately parabolic distribution; higher flexibility ratios generally result in larger deformations of structures; a significant impact on tunnel deformation during large earthquakes is caused by relative slippage between soil and tunnels. The intrinsic relationship between the vertical displacement, earth pressure, relative slippage and strain was investigated to provide a basis for the seismic rescue and seismic design of tunnels.