高地温引水隧洞围岩热——应力耦合分析

针对新疆某高地温环境下的圆形隧洞,采用有限元分析程序,分别对不同围岩半径下的温度场分布进行模拟,并以不同围岩半径下围岩与支护接触面处的温度作为围岩合理计算范围取值的参考,结合有关理论分析的结果,确定出围岩最佳计算半径。在此基础上进一步研究隧洞施工期围岩温度、应力和位移场在热—应力耦合作用下的分布问题。研究结果表明,当围岩外部温度为80℃、隧洞内部温度为5℃时,隧洞开挖后考虑温度和应力共同影响下的围岩最佳计算半径为24 m。隧洞围岩温度沿围岩厚度方向呈非线性递增变化。与常温(20℃)情况相比,高地温的存在会使隧洞围岩最大主应力减小,同时也会在隧洞拱顶和底拱处产生拉应力。

Analysis on thermo-stress coupling of surrounding rock for water diversion tunnel under high ground temperature

For a circular tunnel under the environment of high ground temperature in Xinjiang， the temperature distributions under the conditions of different radiuses of surrounding rock are respectively simulated， and then the temperatures under the conditions of different radiuses of the surrounding rock and at the supporting interfaces are taken as the references for selecting the values within the reasonable calculation range， while the optimal calculation radius of the surrounding rock is determined in combination with the result from the relevant theoretical analysis. On the basis of this， the distributions of the surrounding rock temperature， stress and displacement field under the effect of the thermo-stress coupling during the construction of the tunnel are further studied. The study result shows that when the external temperature of surrounding rock is 80 ℃ and the internal temperature of the tunnel is 5 ℃， the optimal calculation radius of the surrounding rock is 24 m under the consideration of the common effect from both the temperature and the stress after the excavation of the tunnel. Moreover， the tunnel surrounding rock temperature nonlinearly and incrementally changes along the direction of the thickness. Compared with the normal temperature （20 ℃） condition， the existence of high ground temperature can make the maximum principle stress of the surrounding rock decrease， and simultaneously can produce tensile stresses at both the vault and the bottom arch of the tunnel as well.