Assessment On The Safety Of Primary Lining Of Tunnels With Consideration Of Thermal Stress

To a tunnel under construction, a prompt assessment to the safety of the lining through in-situ measured data is of practical importance both for the dynamic design and to guarantee the stability of the tunnel. Among all the parameters measured during tunnel construction, displacement is widely used and thus accepted as a very essential quantity, due to its advantages in convenience, low cost and high credibility.In terms of the displacement-based method previously proposed to evaluate the safety of tunnel support structures, the influence of temperature of shotcrete on the stability of tunnels is approached in this paper. The properties of shotcrete on temperature are discussed, and the formulas to calculate the internal forces of the shotcrete lining with temperature considered are derived out. Then a performance function for the failure of a cross section is given. At last, three case studies are done.The results show that the method gives lower reliability index when temperature of the shotcrete are taken into account. That is to say, the reliability index was unsafe when temperature is neglected. When the temperature difference are low, the influence of temperature is small. However, when the temperature difference arise, the influence of temperature goes up,which should be taken into consideration.This work improves the accuracy of the displacement-based method.