寒区引水隧洞围岩冻胀特性分析——以新疆布伦口水电站引水隧洞工程为例

Analysis of Surrounding-Rock Frost-Heaving Characteristics of Diversion Tunnel in Cold Region:a Case Study on Diversion Tunnel Project of Bulunkou Hydropower Station in Xinjiang

为解决寒区水工隧洞围岩在低温作用下孔隙水相变引起的冻胀问题,以新疆布伦口水电站引水隧洞工程为依托,基于弹塑性力学理论,采用有限元建模分析方法,考虑低温水-冰相变引起的围岩热力学参数变化,使用有限元软件建立温度-渗流-应力耦合模型,计算围岩冻胀力弹塑性解析解及围岩瞬态温度场、冻胀应力和位移,分析冻深变化规律以及冻胀前后的应力变形规律。研究结果表明:1)受低温影响围岩孔隙水发生相变,冻结圈随时间推移向围岩内部移动,冻深随之增大,且冻结计算时间200 d内最大冻深为2.04 m;2)围岩受冻胀作用后的应力为0.392~0.527 MPa,较冻胀前相比有一定幅度的增长;3)围岩水平位移变为-0.36 mm,竖直位移由冻胀前的-9.59 mm变为-8.41 mm,围岩状态表现为水平收缩0.36 mm、拱顶沉降1.18 mm。

In cold regions,frost-heaving phenomenon often occurs due to the phase change of pore water in the surrounding rock of a hydraulic tunnel under the influence of low temperature.First,a thermo-hydro-mechanical coupling model for Bulunkou hydropower station in Xinjiang is established using numerical simulation software based on the theory of elastoplastic mechanics and by considering the change in the thermodynamic parameters of the surrounding rock due to the low temperature water-ice phase change.Subsequently,the elastoplastic frost-heaving force solution of the surrounding rock,transient temperature field,frost-heaving stress,and surrounding-rock displacement are calculated.Finally,the change patterns in the frost depth and the stress and deformation before and after frost heaving are obtained through analysis.The results show the following.(1)The pore water of the surrounding rock undergoes a phase change under low temperature,and the freezing-circle moves to the interior of the surrounding rock over time.The freezing depth increases with time,and the maximum freezing depth is 2.04 m under 200 days of freezing.(2)The calculated stress of the surrounding rock is between 0.392 and 0.527 MPa,and the stress increases compared with that before the frost heaving.The horizontal displacement of the surrounding rock is-0.36 mm,and the vertical displacement varies from-9.59 to-8.41 mm.The states of the surrounding rock in terms of horizontal contraction and arch settlement are 0.36 and 1.18 mm,respectively.