Study On The Temperature Field Distribution And The Influence On The Stability Of Lining Structure Of Tunnel In Qinghai Tibet Plateau

The dissertation conducts the numerical simulation of stress field-temperature field coupling on basis of the ideal elastic-plastic model of Mohr-Coulomb yield criterion relying on the engineering example of Era Mountain Tunnel from Gonghe to Yushu,and a series of studies on the temperature field of the tunnel under the harsh environmental conditions of the Qinghai-Tibet Plateau and the factors affecting the stability of the lining are also finished.The degree of influence of various factors are presented and the conclusions will play a directing role on the construction of tunnel in cold area.In this paper,the numerical simulation of tunnel temperature field is carried out taking advantage of the finite element model of different depth tunnels,the temperature fields of surrounding rock and lining are analyzed under multiple operating conditions.It turns out that the maximum and the minimum temperature differences of the bottom axis of the lining increase with the depth,and the temperature change rate is slow in the beginning and fast afterwards.The temperature changes fastest 40 m away from the entrance of tunnel,and the bottom temperature of the lining is obviously higher than the top.The numerical simulation of tunnel deformation and stress is carried out,and the principal stress and displacement of different lining materials are analyzed under multiple operating conditions.The stress concentration and maximum displacement is prone to happen in the position of the shoulder and arch of the lining.Considering the temperature stress,the magnitude of stress is greatly increased and the stress mainly behaves the tensile,while the value and the distribution of displacement remain unchanged.Finally,the influencing factors are studied,and the variation principles of temperature,stress and displacement distribution of tunnel lining under important parameters are calculated,and the main factors affecting tunnel lining performance are discussed.The main factors affecting the stability of the composite lining structure are temperature difference,followed by the coefficient of linear expansion and the friction coefficient of the contact surface.