在分析钻爆法和TBM法开挖下围岩应力状态的基础上,基于锦屏二级水电站深埋隧洞微震监测数据,对比研究了钻爆法和TBM法开挖条件下深埋隧洞的微震特性及岩爆风险。结果表明:1钻爆法开挖引起的围岩应力集中距洞壁较远,形成的应力梯度较小;而TBM法开挖引起的围岩应力集中临近洞壁,形成的应力梯度较大。2钻爆法开挖时围岩应变能主要集中在爆破后数小时,尤其是在1 h内释放,而TBM法以连续的方式开挖卸载,剧烈的能量释放伴随着施工全过程。3TBM法开挖导致的事件震级及震源破裂尺度均比钻爆法开挖引起的大。4钻爆法开挖时,围岩积聚的应变能大多以岩体破裂的形式耗散,以岩爆形式显现的较少;而TBM法开挖时,围岩应变能常逐次释放,导致事件频繁发生,而且部分应变能以岩爆形式显现,一般地,同一小范围内常多次发生轻微岩爆,高等级岩爆孕育过程中常伴有低等级岩爆,如中等岩爆发生前伴有轻微岩爆,强烈岩爆孕育过程中伴有轻微和(或)中等岩爆,以此类推。综合上述研究结果认为,在具有强岩爆风险的深埋隧洞中,就防治岩爆而言,钻爆法优于TBM法。
Based on the stress state analysis and microseismic monitoring data of the surrounding rock of JinpingⅡHydropower Station, microseismic characteristics and rockburst risk of deep tunnel constructed by TBM-drilling and blasting method are compared and studied. The results show that:(1) The stress concentration of the surrounding rock caused by the drilling- blasting method is far more away from the tunnel wall than that by TBM, and the stress gradient is small, while the stress gradient caused by TBM excavation is large.(2) The strain energy of the surrounding rock mainly releases in several hours after blasting, especially in the first hour. Under the condition of TBM excavation, the stress of the surrounding rock unloads with the continuous mode and the energy violently releases in whole construction process.(3) The Microseismic magnitude and seismic source fracture scale caused by TBM excavation are larger than those by drilling-blasting method.(4) By the drilling-blasting method, the strain energy of the surrounding rock rarely dissipates in the form of rockburst but mostly in the form of rock mass cracking. By TBM excavation, the strain energy of the surrounding rock successively dissipates, resulting in frequent microseismic events. Part of strain energy can dissipate in the form of rockburst. Generally, mild rockbursts often occur in the same range. The inoculation process of high-grade rockburst accompanies with the occurrence of low-grade rockburst. For instance, the occurrence of medium rockburst accompanies with mild rockburst and strong rockburst accompanies with medium rockburst and mild rockburst, and so on. In conclusion, the drilling-blasting method is superior to TBM for rockburst prevention and control of deep tunnel with strong rockburst risk