High Temperature Cracking Mechanism of Surrounding Rock Due to TC and CTE Heterogeneity

Abstract

The entrance section of the high-speed railway tunnel in southern China has been in a state of high temperature for a long time and is subject to alternating temperature changes. The surrounding rock is heterogeneous characteristics. Under a large temperature difference environment, temperature stress will occur between mineral particles and mineral particles. When the temperature stress is greater than the tensile strength of the surrounding rock, it will cause the rock to crack. In order to analyze the mechanism of the tunnel surrounding rock crack disease:(1)Based on thermoelastic mechanics and Weibull distribution, considering heterogeneous of the coefficient of thermal expansion(CTE) of mineral cells, an improved hightemperature initiation mechanical model of heterogeneous rock is established.(2)Aiming at the heterogeneous of thermal conductivity(TC) of mineral cells, the Agari series-parallel model is introduced to improve the thermal conductivity of the model.(3)By changing the degree of heterogeneous of CTE and TC, considering the joint action of the local temperature gradient of the rock, the macroscopic and mesoscopic laws of the initiation mechanism of rock are studied.( 4)Analyze the maximum principal stress and crack initiation temperature regions of sandstone and granite through engineering calculation examples. The results show that with the continuous increase of temperature load, the internal stress of the rock continues to increase. Under the action of temperature load, the peak strength of the rock increases with the increase of the rock homogeneity coefficient. Local