浅埋黄土隧道中系统锚杆支护作用的数值模拟

为了研究系统锚杆在浅埋黄土隧道中的支护效果,以陕西吴堡—子洲高速公路刘家坪5号隧道为依托,利用MIDAS/GTS有限元分析软件分别建立有、无系统锚杆的分析模型,计算分析了6个开挖阶段和截止到二衬施作阶段的隧道变形量,并将数值模拟结果与实测结果进行了对比分析。结果表明:浅埋黄土隧道施工过程中,有系统锚杆的隧道变形值大于无系统锚杆的变形值,这是由于锚杆是在钢架支设后进行打设,锚杆的打设不仅破坏了土体的稳定,而且延误了喷射混凝土和钢架支护的最佳时机,使变形量增加;有、无系统锚杆拱顶下沉和净空收敛的现场实测值基本处于同一数量级,说明在浅埋黄土隧道中系统锚杆的作用不显著,可以取消。

Numerical simulation of support action of systematic anchorage bolts in shallow-buried loess tunnel

In order to study the actional function of systematic anchorage bolts in shallow-buried loess tunnel,this paper taking Liujiaping 5# tunnel of Wubao—Zizhou freeway as an example,two-dimensional plane models with systematic anchorage bolts and without systematic anchorage bolts were established by using the finite element analysis software MIDAS/GTS.In the process of numerical analysis,the displacement amounts were simulated during the six excavation stages and the stage before secondary lining construction,and the numerical simulating results were compared with the ones of measuring.The results show that the displacement of the model with systematic bolts is bigger than that of the model without systematic bolts during the construction of shallow-buried loess tunnel,because the rock bolts are constructed after steel arch.Construct-ing the anchorage blots,not only the stability of soil mass is broke,but also the best time of constructing shotcrete and steel support is delayed.Moreover,both the two modes have almost the same settlement in the tunnel arch crown and horizontal convergence during in-situ test.Through comprehensive analysis,it is found that the role of systematic anchorage bolts is not obvious in shallow-buried loess tunnel and can be eliminated.