Similar simulation experiment of expressway tunnel in karst area

•Tunnel lining and the surrounding limestone rock were studied by similarity theory and orthogonal tests.•The design, structure, and manufacturing methods for lining, test device, and karst cave were studied.•Different test cases were designed to analyze the parameters of the designed model.•The designed model satisfies the constraints, simulates the rainfall conditions.•The designed model can be used to simulate the effect of karst cave on the tunnel. According to the actual situation of an expressway tunnel in karst area, the tunnel lining, surrounding rock, and test model were designed by a similar theory and orthogonal experiment. The similarity constants were determined from similar material design experiments. The similar mixture ratio of simulated limestone and tunnel lining was determined using uniaxial compression, triaxial and Poisson's ratio tests. Based on these tests, the structures of lining and karst cave models were designed and analyzed. The data of experimental model were acquired using pore pressure, soil pressure and displacement measuring instruments. Considering the rock joint occurrence, size of cave, cave location, precipitation, loading and other parameters, the pore water pressure, earth pressure, and displacement sensor of experimental model were analyzed under artificial rainfall and loading conditions. The results show that the development of a karst cave affects the tunnel water flow. The test results also show that the experimental model can simulate water penetration and calculate water content.