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金沙江白鹤滩水电站导流洞III1类柱状节理玄武岩发育,开挖过程中松弛破坏明显,对施工人员安全及施工进度造成严重影响。基于微震监测技术对白鹤滩柱状节理玄武岩导流洞开挖全过程进行研究,沿隧洞轴向方向,柱状节理玄武岩微震活动集中于开挖掌子面附近,服从三参数Logistic分布。掌子面附近及其后方微震活动分布可分为3个区域:开挖强卸荷区、综合影响区和时效松弛区,在开挖强卸荷区范围内应完成锚杆支护。隧洞开挖过程中,柱状节理玄武岩微破裂由隧洞边墙快速向围岩内部发展,当掌子面距离较远时,边墙内微破裂活动较微弱,微破裂集中区最终稳定在距边墙6 m范围内。降低开挖速率能有效减弱开挖卸荷对柱状节理玄武岩的影响。所得认识和结论对微震监测技术的应用以及柱状节理隧洞开挖方案和支护措施的优化具有参考意义。
The development of Class III1 columnar basalt in the diversion tunnel of Baihetan Hydropower Station, Jinsha River, with obvious relaxation and destruction during excavation, has a serious impact on the safety of construction workers and the progress of construction. Based on the microseismic monitoring technique, the whole process of excavation of the basalt dike tunnel in Baihetan was studied. The microseismic activities of columnar jointed basalt along the axial direction of the tunnel centered on the face of excavation face and obeyed the Logistic distribution of three parameters. The distribution of microseismic activity near and behind the face of the face can be divided into three regions: strong unloading area for excavation, comprehensive impact area and time-lag relaxation area, and the bolt support should be completed within the range of strong unloading area for excavation. During the process of tunnel excavation, the micro-rupture of columnar jointed basalt rapidly develops from the side wall of the tunnel to the interior of the surrounding rock. When the face of the tunnel is far, the micro-rupture activity in the side wall is weak. Finally, the micro- 6 m range. Decreasing the excavation rate can effectively reduce the influence of excavation and unloading on columnar jointed basalt. The obtained cognition and conclusion have reference significance to the application of microseismic monitoring technology and the optimization of tunnel excavation scheme and support measure of columnar joint.