A Theory On Dynamicresponse Of Unsaturated Soil Under Moving Loads

In recent years, with the rapid development of high-speed railway and highway, studies of the dynamic response of foundation under the action of moving loads has drawn wide attention by related scholars. It is well known that high-speed railway and highway are very strict with settlement of foundation. And the settlement of foundation has a closely relation with moving load, track system and type of foundation. Based on this, the detailed research and exploration to the dynamic response of saturated foundation, unsaturated foundation and track and unsaturated foundation coupled system under moving load was carried on.Firstly, combined with the Biot’s dynamic governing equations for saturated soil and by making use of Fourier transform and Cauchy-Reimann conditions, the integral form solutions of displacement and stress for a saturated half-space under moving loads were obtained. By means of the inverse Fourier transform and numerical analysis, the combined effects of the speed, frequency of moving load and efficient of permeability of saturated soils on dynamic response were analyzed.In this paper, the dynamic response of track and unsaturated foundation coupled system under moving load was studied by using analytical method. The rails were described as an infinitely long Euler beam. And the impact of sleepers and ballast were taken into account. By using the dynamic equations of track and the underlying unsaturated soils in Fourier transform domain, the integral form solutions of displacement and stress for the coupled system under moving loads were obtained. Lastly, the combined effects of saturation of unsaturated soils and rail rigidity on dynamic response were discussed by numerical calculation.Natural foundation is made of complex three-phase materials. Generally speaking, the soil below water level can be approximately considered as saturated soil. However, the soil above water level contains a lot of gas. So, the soil above water line should be considered as unsaturated soils. In view of this, the relative research work was carried out. By means of the dynamic equations of Biot’s dynamic governing equations for saturated soil and the dynamic governing equations of unsaturated soils in Fourier transform domain, the integral form solutions of displacement and stress for a saturated half-space with an unsaturated superstratum under harmonic loads were obtained. By means of the inverse Fourier transform and numerical analysis, the combined effects of the unsaturated superstratum’s saturation, thickness and the exhaust-drainage situation of ground surface on dynamic response were analyzed.