超大断面隧道施工围岩-支护结构稳定性研究

Study on stability of rock supporting structure during construction of super-large cross-section tunnel

通过设计和实施现场监测试验,对姚家峪超大断面隧道施工过程力学进行研究。结合数学统计分析方法,研究了超大断面隧道以半步CD法施工过程中围岩-支护结构的稳定性。通过对围岩荷载、初支结构应力和锚杆轴力的时空演化规律进行分析得到以下结论:①掌子面开挖到监测断面后的第0~10天为隧道施工危险期,应加强这一施工阶段的落石、垮塌等风险的排查;②拱顶围岩荷载最大且较稳定,中线左侧围岩荷载大于右侧围岩荷载,有明显的偏压现象,应当加强对左洞左侧洞体的监控量测;③初支结构应力空间分布图表现为不规则的“M”形,其分布规律为拱顶初支结构应力最大,左右呈不对称分布;④锚杆轴力在空间上的分布差异较小,隧道整体结构稳定性较好。

By design and implementation of field monitoring test,the construction process of Yaojiayu super-large cross-section tunnel was monitored on site,and the stability of surrounding rocks-supporting structure of the tunnel was studied by statistics analysis.Based on the analysis on the time series change law and spatial distribution law of surrounding rock load,initial support structure stress and anchor bolt axial force,it is concluded that:①the danger period of tunnel construction is 0~10d after the excavation of the palm-face comes to the monitored section,and the risk of rockfall and collapse in this stage should be screened.②the surrounding rock load of the vault is the largest and relatively stable,the load of surrounding rock on the left side of the middle line is larger than that on the right side,manifesting obvious bias phenomenon,so the monitoring and measurement of the left side of the left tunnel should be strengthened.③the spatial distribution of stress of the early support structure shows an irregular"M"shape,and the early support structure at the vault has the maximum stress with an asymmetrical distribution from the left to right.④the spatial distribution of bolt axial force has less differences,and the overall structure of the tunnel is stable.