DYNAMIC CHARACTERISTICS OF NEARLY SATURATED VISCOELASTIC SOIL AND LINING SYSTEM WITH A TUNNEL

The lining and soil skeleton are respectively treated as a porous elastic material and a viscoelastic medium with fractional derivative constitutive relations. The influences of the water saturation on the dynamic characteristics of the fractional derivative viscoelastic nearly saturated soil and elastic lining system with partial sealed tunnel are investigated in the frequency domain. The mixture of water-gas is considered as a homogeneous fluid. By the Boit’s theory and elastic one, the analytical expressions of displacement, stress and pore water pressure of the nearly saturated viscoelastic soil and lining are respectively obtained subjected to the harmonic axisymmetric load or fluid pressure. By utilizing the inner boundary condition of the lining and the continuity conditions between the soil and the lining, the specific expressions of undetermined coefficients are determined. It is found that the effects of the relative permeability coefficient of lining and soil on the pore water pressure amplitude are related to the value of water saturation; the displacement amplitude increases with the water saturation decreasing under the fluid pressure. In addition, the parameters of fractional derivative model have great impacts on the system dynamic responses.