Abstract:In order to study the mechanical characteristics of the elastoplastic zone of the surrounding rock of circular hydraulic tunnel, based on the Mogi-Coulomb(Mogi-Coulomb) strength criterion and the elastoplastic theory, considering the effects of temperature and lining structure, the analytical solutions of surrounding rock stress, wall displacement and surrounding rock plastic zone radius of hydraulic tunnel under thermal mechanical coupling are deduced. Relying on the highland temperature hydraulic tunnel project in Xinjiang, the calculation and analysis are carried out, the relationship between the intermediate principal stress coefficient, temperatures, concrete strength, lining thickness and surrounding rock stress distribution and plastic zone radius is analyzed. The following conclusions are drawn: 1) The tensile stress caused by temperature change will reduce the support reaction of the lining structure to surrounding rock, the radius of plastic zone of surrounding rock and the displacement of tunnel wall will increase, and stability of the surrounding rock will be worse; 2) The intermediate principal stress coefficient has a greater impact on the strength of the surrounding rock. When b=0.5, the radius of the plastic zone of the surrounding rock is obviously smaller than without considering the intermediate principal stress; 3) The improvement of concrete strength and the increase of lining thickness can obviously limit the development of plastic zone of surrounding rock in the initial stage. Although the follow-up effect is not good for limiting the development of plastic zone of surrounding rock, increasing the lining thickness can more restrict the development of plastic zone of surrounding rock.