既有隧道不同扩挖宽度下锚杆参数的优化

Optimization of rock bolt parameters for existing tunnel with different expansion widths

以黄山洞隧道工程为依托,通过对现场数据的监测和利用有限元分析软件Midas GTS NX进行数值模拟,分析了不同扩挖宽度下隧道拱顶沉降值、周边收敛值和围岩有效应力变化的规律,并改变锚杆的长度和锚杆间距,分析在不同锚杆长度下围岩有效应力、衬砌应力以及锚杆应力的变化规律,确定了不同扩挖宽度下最优的锚杆长度和锚杆间距.研究结果表明:随着扩挖宽度的增加,围岩有效应力由大至小依次为拱脚处压应力、拱腰处压应力、拱顶处压应力和仰拱处拉应力;拱顶处压应力随扩挖宽度的增大而减小,拱腰处压应力随扩挖宽度的增大而增大,但增大趋势不明显;受单侧扩挖方式的影响,扩挖侧的应力大于非扩挖侧;拱脚处受到应力集中的影响,其压应力随着扩挖宽度的增大而增大;扩挖宽度为1.5~2.5 m时的最优锚杆长度和间距分别为2.5 m和1.7 m,扩挖宽度为3.5~4.5 m时二者分别为3.0 m和1.2 m.

Based on Huangshandong Tunnel project,field data monitoring and numerical simulation by finite element analysis software of Midas GTS NX were used to analyze the laws of vault settlement,peripheral convergence and effective stress change of surrounding rock under different expansion widths.The length and ring distance of anchor bolts were changed to discuss the variation laws of effective surrounding rock stress,lining stress and bolt stress under different bolt lengths,and the optimal bolt length and bolt spacing under different expansion widths were determined.The results show that the decreasing sequence of effective surrounding rock stress is the compressive stress at the arch foot,the compressive stress at the arch waist,the compressive stress at the arch top and the tensile stress at the invert.With the increasing of excavation width,the compressive stress at the top of arch is decreased,while the compressive stress at the waist is increased with unconspicuous increasing trend.Under the influence of the single-side expansion mode,the stress of expansion side is greater than that of the non-expansion side.Due to the influence of stress concentration,the compressive stress at the arch foot is increased with the increasing of excavation width.For the expansion width of 1.5-2.5 m,the length and spacing of the anchor rod are respective 2.5 m and 1.7 m,and for the expansion width of 3.5-4.5 m,the length and spacing of the anchor rod are respective 3.0 m and 1.2 m.