高地温条件下深埋隧洞围岩温度—应力分析及施工对策

以位于西昆仑山区的齐热哈塔尔水电站引水发电隧洞高地温洞段为例,初步分析了工程区隧洞高地温洞段大地热流背景及其形成机理,针对隧洞围岩的高地温分布特征,建立典型高地温洞段地质模型,利用有限元软件模拟隧洞施工贯通通水后的围岩岩体温度场,并由此来推断热应力对于围岩稳定性的影响。结果表明,围岩温度90℃以上、空气温度50℃以上的高地温洞段,内外温差大于10℃(里低外高),若采用无衬砌和一次支护方案对高地温洞段围岩进行支护,该洞段内大部分区域的最大主拉应力将超过C25混凝土的抗拉强度,易产生整体拉裂破坏;若采用钢筋混凝土衬砌结构方案,则可以通过增加衬砌结构的配筋量来降低其最大主应力值,此时隧洞围岩及衬砌结构均未出现整体拉裂破坏。研究成果能够为保证该高地温隧洞的安全运行提供可靠的设计依据。

Temperature-stress analysis on surrounding rock of deeply buried tunnel under condition of high ground temperature and its construction countermeasures

By taking the high ground temperature section of the intake tunnel for Qireha Starr Hydropower Station located in the area of the West Kunlun Mountains as the study case，the terrestrial heat flow background and forming mechanism of the high ground temperature section of the tunnel within the project area are preliminarily analyzed herein，and then a geological model for the typical high ground temperature tunnel section is established for the high ground temperature distribution characteristics of the tunnel surrounding rock，from which the temperature field of the surrounding rock after the tunnel holing-through and water intaking is simulated with the finite element software，and on the basis of this，the impact from the thermal stress on the stability of the surrounding rock is deduced as well. The result shows that in the high ground temperature tunnel section with the surrounding rock temperature above 90 ℃ and the air temperature above 50 ℃，if the surrounding rock of the section is supported by the supporting schemes of non-lining and primary support，the maximum principal tensile stress in most of the area in the tunnel section is to exceed the tensile strength of the C25 concrete and then is prone to cause an overall tensile failure，when the inside and outside temperature difference （lower inside and higher outside） is larger than 10 ℃. However，if the scheme of reinforced concrete lining structure is adopted，the maximum principal tensile stress therein can be lowered through increasing the amount of reinforcement，thus no overall tensile failures of both the tunnel surrounding rock and the lining structure are to be caused under this circumstance. The study result can provide a reliable design basis for guaranteeing the permanent safe operation of the high ground temperature tunnel.