管棚布设范围对软岩隧道围岩稳定性影响研究

Influence of Pipe Roof Layout Range on Stability of Surrounding Rock of Soft Rock Tunnel

为确保管棚布设在软岩隧道中起到良好的支护效果,依托蓝家岩特长公路隧道,采用数值模拟与模型试验相结合的方法研究管棚布设范围对软岩隧道围岩稳定性的影响规律。研究结果表明:1)在管棚其他参数保持不变的情况下,随着管棚布设范围的增大,拱顶沉降的最终值呈现出近似单调减小的趋势,拱脚收敛的最终值呈现出非线性减小的趋势。2)管棚布设范围由90°增大到180°时,拱顶沉降的最终值由-0.389m减小至-0.317m,降低幅度达18.5%;而拱脚收敛的最终值由-0.486m减小至-0.355m,降低幅度达26.9%。3)加大管棚布设范围能够有效控制围岩变形,提高管棚的支护效果,且管棚布设范围的改变对拱脚收敛的影响程度大于拱顶沉降。对比分析不同管棚布设范围条件下的数值模拟及模型试验结果,得到的洞周围岩变形随管棚布设范围的规律是一致的,且2种方法得到的各工况下洞周变形的量值较为接近。

The supporting effect of pipe roof in Lanjiayan extra-long soft rock highway tunnel should be guaranteed. Hence, the influence of pipe roof layout range on stability of surrounding rock of soft rock tunnel is studied by numerical simulation and model test. The study results show that:(1) With the increase of the layout range of pipe roof, the settlement of tunnel crown decreases approximately monotonously, and the ultimate convergence of arch feet shows a nonlinear decreasing trend when other parameters of pipe roof remain unchanged.(2) When the layout range of pipe roof is increased from 90° to 180°, the final crown settlement decreases from -0. 389 m to -0. 317 m, with a reduction rate of 18. 5%, while the final convergence of arch feet decreases from -0. 486 m to -0. 355 m, with a reduction rate of 26. 9%.(3) By enlarging the layout range of pipe roof, the deformation of surrounding rock can be effectively controlled and the supporting effect of pipe roof can be improved;the influence of changing the layout range of pipe roof on the convergence of arch feet is greater than that of the crown settlement. By comparing and analyzing the numerical simulation and model test results under different pipe roof layout conditions, the conclusion that deformation laws of rock around the tunnel obtained by the two methods coincide with each other, and the values of deformation around the tunnel obtained by the two methods under different working conditions are close to each other can be drawn.