浅埋偏压大跨花岗岩残积土小净距隧道合理间距研究

Reasonable distance for super-large section neighborhood tunnel of granite residual soil with shallow–buried bias

针对花岗岩残积土浅埋偏压大跨小净距隧道合理间距与偏压程度的关系问题,引入偏压率P,通过建立洞口段1:7,1:5和1:3共3种边坡坡度的偏压小净距隧道模型;基于FLAC3D软件,研究花岗岩残积土围岩小净距隧道施工工法优化和不同偏压率P对其最小合理间距的影响。研究结果表明:双侧壁导坑法较适合偏压率为1.13的小净距隧道施工,最小合理间距为24 m,中间岩柱是最薄弱部位;岩柱上方地表沉降最大,靠近岩柱两侧隧道支护锚杆轴力最大,在施工过程中塑性变形较严重,进一步验证了数值模拟结果的合理性,因此,在施工时应优先加固岩柱的上岩盘,同时兼顾加固中岩盘和下方岩盘,确保中间岩柱稳定。

In order to discuss the relationship between reasonable spacing and degree of bias of granite residual soil shallow–buried bias tunnels with small spacing span, the bias ratio index P was introduced. After the tunnel portal of bias neighborhood tunnel models were built for three kinds of slope gradient, i.e. 1：7, 1：5 and 1：3, the impact of granite residual soil surrounding rock tunnel construction methods optimization and different rates of bias P on the reasonable minimum spacing were discussed based on the software FLAC3 D. The results show that the double side heading tunnel construction method is more suitable for bias of 1.13, and that the minimum reasonable distance of tunnel is 24 m, the middle pillar is the weakest part, the settlement of pillar above the group is the largest, the axial forces of the supporting bolt of both sides of the tunnel are the largest, and during the construction process the plastic deformation of both sides near the pillar is also the biggest. The numerical simulation method is feasible and effective; therefore, the rock on the plate of rock pillar must be firstly consolidated during tunnel construction, and rock both in the middle and under the plate must be consolidated to ensure the stability of the middle rock pillars.