浅埋大断面分岔隧道中夹岩柱稳定性数值模拟研究

Numerical Simulation Study on Stability of Intercalated Rock Columns in Shallow-buried Large-section Bifurcation Tunnel

大断面分叉隧道的中夹岩柱厚度较薄、施工工序转换较多、岩体受力较为复杂。以某大断面分叉隧道为工程背景,首先根据现场围岩实际变形,借助有限差分软件FLAC 3D进行反演,得到了围岩弹性模量E,然后根据反演参数对隧道开挖进行数值模拟研究。得出如下结论:(1)中夹岩柱的厚度对两侧隧道上部岩体的沉降变形影响较大,岩柱厚度越薄,两侧隧道拱顶沉降变形越大,同时围岩变形越集中于岩柱上方;(2)中夹岩柱厚度越薄,岩柱岩体竖向应力、剪应力越大,受力机理越复杂,但岩柱竖向最大压应力与最小剪应力均没有超过其承载范围;(3)岩柱厚度越薄,两侧隧道拱腰处初期支护受压越严重,但支护结构受力较为均匀,无明显的偏压现象。将计算结果与现场实际监测数据进行对比分析后发现吻合较好,可为类似工程实践提供一定参考。

The large-section forked tunnel has intercalated rock columns of unfavorable thickness, frequently-transferred construction procedures, and complicated stress of rock mass. Taking a large section forked tunnel as engineering background, firstly, according to the actual deformation of the surrounding rock on site, the elastic modulus E of the surrounding rock is obtained by inversion with the help of finite difference software FLAC 3D, and then, according to the inversion parameters, the tunnel excavation is numerically simulated.The results are as follows :(1) the thickness of the intercalated rock columns has a great influence on the settlement deformation of the upper rock mass on both sides of the tunnel. The thinner the intercalated rock columns are, the greater the settlement deformation of the vault on both sides of the tunnel is, and the surrounding rock deformation is more concentrated above the rock pillar;(2) The thinner the intercalated rock columns are, the greater the vertical stress and shear stress of the rock pillar are, and the more complex the mechanical mechanism is, but the maximum compressive stress and minimum shear stress of the rock pillar do not exceed their bearing range;(3) The thinner the intercalated rock columns are, the more serious the initial support compression is at the arch waist of both sides of the tunnel, but the support structure is more uniform and there is no obvious bias. The calculated results are in good agreement with the actual monitoring data after comparative analysis, which has certain guiding significance for engineering practice.