Dynamic Response of Layered Unsaturated Soils under Moving Loads

Based on the theory of porous media mixture, a computational model of two-dimensional layered unsaturated soil foundation is established and the dynamic response of layered unsaturated soil under moving load is studied. The stiffness matrix of the layered unsaturated soil foundation is obtained by the Fourier transform and Helmholtz vector decomposition principle and the numerical solutions of the layered unsaturated soil foundation in the frequency domain are solved by using the transfer matrix method and combining the boundary and interlayer continuity conditions in the derivation. The numerical solutions of displacement, stress, and pore pressure in the layered unsaturated soil are obtained by Fourier inversion. The numerical examples were used to analyze the effects of load velocity, shear modulus, and saturation on the dynamic response of two typical layered foundations: upper soft and lower hard foundations, and upper hard and lower soft foundations, respectively. The results show that when the load movement velocity is close to the shear wave velocity in unsaturated ground and causes the resonance of the soil, the vertical displacement of the surface increases rapidly to the peak; the order of the soil layers in the layered unsaturated ground has a significant effect on the surface displacement, and the vertical displacement of the upper soft and lower hard foundation is larger than that of the upper hard and lower soft foundation; the saturation degree has a significant effect on the dynamic response of the layered unsaturated ground. The saturation degree has a significant effect on the dynamic response of the layered unsaturated foundation, and the surface vertical displacement increases with the increase of the saturation degree of the surface soil in both the upper soft and lower hard foundation and the upper hard and lower soft foundation.