关键词: 超大断面隧道, 围岩支护, 结构稳定性, 半步CD法施工, 现场监测试验,

Abstract: 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:(1) the 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.(2) the 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.(3) the 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.(4) the spatial distribution of bolt axial force has less differences,and the overall structure of the tunnel is stable.

Key words: super-large cross-section tunnel, rock supporting structure, structure stability, Upper-Bench CD method, field monitoring test,