In this paper

loading-unloading experiments were carried out on gas-contained coal under different stress levels by using self-made thermal-hydro-mechanical (THM) coupling equipment. The characteristics of the deformation

seepage and energy dissipation of coal and rock were analysed

and the damage variable equation was also established by considering the energy dissipation. Research results show that the cumulative residual deformation increases gradually with the advancing of cyclic loading-unloading. The relative residual deformation decreases firstly

then maintains stable at a certain value

and finally rises again when the coal sample is nearly destroyed. With the advancing of cyclic loading-unloading

the overall trend of permeability decreases spirally

and then increases until the coal sample is fractured. Moreover

a sharp increase is observed at the moment of destruction. The absolute recovery rate of permeability and relative recovery rate of permeability are defined as ?j and ?x to quantitatively analyse the changes of permeability in loading and unloading processes

respectively. It is found that ?j decreases firstly

and then increases at the critical moment of destruction. However

?x increases steadily during the process

where ?x maintains at 85%-95% in the elastic stage

and ?x is more than 100% at the critical moment of destruction. With the advancing of cyclic loading-unloading

the cumulative dissipated energy grows exponentially

and the single-stage cycle of dissipation energy increases. With the increase of the axial stress

the principal stress difference increases

and the value of damage variable also increases. In addition

damage variable of coal Dc is 0.9 when coal is fractured.