Abstract: Deep underground rock is often subjected to the coupled actions of temperature field, seepage field and stress field. In this paper, the thermal-hydro-mechanical coupling characteristics of clay rock are studied via experimental and theoretical approaches. First of all, triaxial compression tests were conducted at different temperatures to reveal the relationship among temperature, deformation, and permeability as follows: high temperature deteriorated the internal structure of clay rock in a qualitative sense by degrading peak strength and raising strain deformation; permeability coefficient firstly declined and then increased along with deformation, and decreased slightly in post-peak stage, respectively corresponding to three stages (volumetric strain compression hardening stage, dilatancy hardening stage, and dilatancy softening stage), with the turning point of volumetric deformation implying the acceleration of permeability; under 50 ℃, the permeability of clay rock reduced with the climbing of temperature, while increased when above 50 ℃, with the real damage developing rapidly. On the basis of such experimental results, a constitutive damage model of clay rock under thermal-hydro-mechanical coupling effect was established, and was verified by experimental results.

Key words: clay rock, temperature-seepage-stress coupling, volumetric strain, permeability coefficient, damage characteristics, constitutive model