流固耦合作用下隧道开挖模拟研究

Study of Tunnel Excavation Simulation Under Fluid-Structure Coupling Action

根据渗流力学、弹塑性力学以及多场耦合理论,构建隧道开挖流固耦合模型。以湖南省湘西州古丈县张吉怀铁路毛坪村隧道施工为例,选取典型断面,采用COMSOL模拟耦合作用下隧道开挖引起的围岩渗流场及塑性区变化规律,并将拱顶沉降值与现场实际观测结果进行对比。结果表明:隧道开挖扰动原岩发生应力重分布,使拱腰和拱底附近塑性区范围发生显著变化;对比不考虑流固耦合作用和考虑流固耦合作用下的模拟结果可知,流固耦合作用下隧道拱腰和拱底处围岩的应力值相对较高,高出的应力值最大可达0.2 MPa,且流固耦合作用下隧道围岩变形稳定后,拱顶沉降值可达55 mm。采取喷砼支护措施后,隧道拱腰和拱底处的应力集中区范围显著减小,隧道拱顶沉降值可降低至26 mm。由此可见,流固耦合作用增加了围岩的应力和位移,支护措施减小了拱腰和拱脚处应力集中区范围和拱顶沉降值。

According to the seepage mechanics,elastoplastic mechanics and the multi-field coupling theory,the fluid-solid coupling model of tunnel excavation is constructed.Take the construction of Maopingcun Tunnel of Zhangjihuai Railway in Guzhang County,Hunan Province as an example,and using COMSOL to simulate the variation law of seepage field and plastic zone of surrounding rock caused by tunnel excavation under the coupling action,and the settlement value of the vault was compared with the actual observation results.The results show that the tunnel excavation disturbs the original rock and the stress redistribution occurs,which makes the plastic zone near the arch waist and the arch bottom and the arch bottom and the arch bottom change significantly.And according to the comparison of the simulation results without considering the coupling effect and considering the fluid-solid coupling effect,the stress values of the tunnel arch waist and the surrounding rock under the fluid-solid coupling are relatively higher,and the maximum higher stress value can be up to 0.2 MPa.In addition,after the deformation of the surrounding rock of the tunnel is stable under fluid-solid coupling,the settlement value of the vault can reach 55 mm.However,after adopting shotcrete support measures,the stress concentration zone of the tunnel arch waist and the arch bottom is significantly reduced,and the settlement value of the tunnel vault can be reduced to 26 mm.So it is obviously that the fluid-solid coupling increases the stress and displacement of the surrounding rock,and the support measures reduce the range of the stress concentration zone of the arch waist and the arch bottom and the settlement value of the vault.