In light of the collapse of an expansive soil tunnel owing to rainfall infiltration

swelling stress field caused by the change in the moisture content distribution of surrounding soil was taken into consideration to solve the problem. At first

due to the similarity of continuum heat conduction energy-balance equation and seepage continuity equation

an alternative expansive equation is derived based on the theory of heat conduction expansive to simulate water-increased expansion of expansive soil

and then determine the swelling force and seepage parameters by laboratory test and engineering simulation. Finally

considering the proper geologic factors

a numerical model of tunnel is established by means of thermal-mechanical coupling of FLAC3D. And by the simulations of tunnel with different swelling forces under water-increased state

relation curves are acquired between liner deformation and moisture content

swelling force. According to the above analysis

turning points of moisture content and swelling force to prevent liner from failure are proposed

which can effectively guide the design and deformation controlling of tunnel liner in expansive soil.