Mechanical properties and thermo-chemical damage constitutive model of granite subjected to thermal and chemical treatments under uniaxial compression

Fire, chemical actions, and other hidden dangers during construction and service often threaten tunnels and other underground structures. This study investigated the strength and deformation properties of granite treated with high temperatures and chemical solutions through uniaxial compression tests. Then, a novel statistical damage constitutive model was defined, which considers the initial thermo-chemical damage and loading damage, to discuss the effects of thermal and chemical treatments on the damage evolution of granite during uniaxial compression. The compaction coefficient is proposed to describe the compaction degree of the pore structure induced by thermo-chemical treatment. It is used to modify the proposed damage constitutive model. Finally, the applicability of the modified model and the sensitivity of compaction coefficient are verified and discussed by laboratory data. The results indicate that high temperatures and chemical actions reduce the uniaxial compressive strength and elastic modulus of granite. The modified constitutive model can effectively reflect the compaction characteristics of pore structure induced by thermo-chemical treatment in the initial loading stage. Within 150 degrees C, the damage caused by chemical treatment is higher than that by thermal treatment. After thermal treatment at 300 degrees C or above, the thermal damage gradually increases, and the difference in chemical damage caused by different solutions decreases. The rising rate of the damage evolution curve gradually slowed down and changed from nonlinear to linear with increased temperatures.