Design and experimental research on model soils used for shaking table tests of superstructure-soil-tunnel interaction system

In order to match the similitude ratio of acceleration of a superstructure-soil-tunnel interaction system and truly restore its dynamic response under earthquake action, a kind of model soil composed of sawdust, river sand, silty clay and water is designed by combining the theoretical analysis with experiments. A large number of resonant column tests on the model soils with different material ratios are carried out at confining pressure of 30 kPa, then the orthogonal test scheme is designed and conducted, and Y(Sγ_r, S_α, Q) function is created to judge the similitude about dynamic shear modulus ratio-shear strain curves between model and prototype soils. The orthogonal test results show that the optimal mass ratio of sawdust, river sand and silty clay is 18%∶27%∶55%, and the moisture content is 50%. The model soil with the optimal proportion basically satisfies the expected target that its similitude ratio of acceleration to the prototype soil is 3 and its correlation curve of dynamic shear modulus ratio-shear strain is similar to that of the prototype soil. The influence laws about dynamic parameters of model soils are obtained for various additive materials. In addition, the resonant column tests on the model soil with the optimal proportion are carried out at confining pressures of 50 and 70 kPa. It is verified that the similitude between the model and prototype soils at different confining pressures is basically satisfied, their correlation curves about damping ratio and shear strain are compared, and it is obtained that their similitude about damping ratio is reasonable. Based on the similarity analysis of the predominant period, the similitude between the model and prototype soils is verified again. The research conclusions may provide some reference for the preparation of model soils in shaking table tests in the future.