Transient Dynamic Response Of Deep Buried Cylindrical Cavity In Unsaturated Porous Media

The study on dynamic response of unsaturated porous medias is an important subject in the field of porous media dynamics and it is significant in theory and valuable in practice. It is found that the theory of dynamic of long linear structure under the transient load is uncommon. Moreover, it is less rare in unsaturated porous media. Therefore, this paper is mainly based on the dynamic theory of unsaturated porous media. After a lot of review, analysis and comparison of the existing literature related to the theory of unsaturated porous media, appropriate control equations are selected. The wave equation is solved by the method of Laplace transformation and inverse transformation. Then the frequency domain and time domain solutions of the dynamic response are obtained when the instantaneous dynamic load acts on the cylindrical cavity (without lining) and the cylindrical lining cavity in unsaturated porous medias. The concrete research about unsaturated porous media deep buried cylindrical cavity will be presented:(1) The solution to the problem of dynamic response of deep buried cylindrical cavity in unsaturated porous medias is obtained. Under two different boundary conditions (a permeable surface and an impermeable surface) and different degrees of initial saturation and porous media skeleton stiffness, the variation of the amplification factor with time on the hoop stress, radial displacement and the pore pressure on the inner surface in the cavity are studied and analyzed. The variation of the circumferential stress, radial displacement and pore pressure in the process of the change of the pore pressure is also studied. It turned out that the effect of saturation on the dynamic response is not obvious when the porous media is hard and the porosity of porous media is low. There is a close relationship between the maximum value of the stress displacement and the change of degree of saturation when the porosity is heavy. In addition, the elastic modulus of the porous media skeleton has a certain influence on the dynamic response. Stress increases with the increase of the stiffness, while the displacement is opposite.(2)The solution to the problem of dynamic response of deep buried cylindrical lining cavity in unsaturated porous medias is obtained. The impact of initial saturation of porous media medium, relative stiffness and the thickness of the lining on magnification factors and the value of hoop stress, radial displacement and pore pressure on the interface between unsaturated porous media and lining were analyzed. Result shows that stress and displacement on the interface between the two reacting are significantly smaller than that of the cavity. Besides the influence of the physical properties of the lining medium on the dynamic response is also obvious. The bigger are the relative stiffness of the lining and the porous media skeleton and the thickness of the lining and the smaller will be the stress and displacement at the interface. Furthermore, the increase of relative stiffness has no effect on the dynamic response when the stiffness ratio exceeds a certain value.