Abstract: Most soils in nature are unsaturated media, however, most of the soil was assumed to be elastic or saturated media in the previous studies on the transient dynamic response of circular lined tunnels. In this paper, considering the dynamic interaction between the soil and the tunnel lining and the additional mass density caused by dynamic load, the transient dynamic response of a deeply buried cylindrical lined tunnel with infinite length in saturated soil is studied. Based on the porous medium mixture theory and continuum mechanics theory, the controlling equations of the tunnel lining and unsaturated soil are derived when the cylindrical lined tunnel is subjected to transient load. The dynamic response of lining and unsaturated soil in time domain is obtained by using Durbin numerical inversion method. The effects of different saturation degrees on radial displacement, radial stress, hoop stress and pore water stress under transient load are presented and discussed. The results show that (a) the saturation degree has a significant influence on the transient dynamic response of lining and unsaturated soil; (b) the saturation degree has a less influence on the radial attenuation of radial displacement, but has greater influence on the radial attenuation of hoop stress and pore pressure.

Key words: unsaturated soil, cylindrical lined cavity, dynamic response, Laplace transform, saturation degree