Abstract: A three-dimensional calculation model of a cylindrical lined tunnel and the surrounding unsaturated soil is established to analyze the response to internal explosion load by assuming that the transient load decays exponentially along the direction of the tunnel. The governing equations of lining structure and surrounding unsaturated soil under blasting load are derived based on the theory of porous media mixture and continuum mechanics. The analytical solutions of tunnel lining and surrounding unsaturated soil in frequency domain and wave domain are obtained by using Laplace and Fourier transform. The effect of saturation on the dynamic response of lining structure under the action of endogenous explosion is considered. The results indicate that the saturation has a substantial effect on the radial displacement of the inner surface of the lining. As saturation increases from 0.15 to 0.98, the radial displacement at the explosion source increases by about 28% in the axial direction. The variation of radial stress on the inner surface of lining with time is not significantly affected by saturation. The crest value of lining’s circumferential stress expands with increasing saturation and the time to achieve the apex is gradually postponed. In the axial direction, as the saturation increases from 0.15 to 0.98, the circumferential stress at the explosion source increases by about 29%.

Key words: transient load, unsaturated medium, lined tunnel, dynamic response, Laplace transform, Fourier transform