基于爆破卸压地应力快速释放的强岩爆防治方法与效果评价研究

Study on Prevention and Control Effect of Strong Rock Burst Based on Rapid Stress Release of Blasting Relieving Pressure Technology

深埋隧洞强岩爆灾害是制约工程开挖施工安全和高效实施的难题,科学爆破开挖设计已成为有效控制强岩爆灾害的重要技术手段。针对锦屏二级引水隧洞工程随隧洞埋深增加、地应力增大所频现的强岩爆灾害的防控问题,对爆破卸压方法的强岩爆防治效果开展了数值仿真设计与现场试验研究。围岩内双排倾斜辐射孔和掌子面垂直超前孔两种爆破卸压方法的数值论证结果表明:前者可在左侧边墙爆破孔及拱顶中部附近、右侧拱腰下部和拱肩爆破孔附近形成了应力松弛区,应力集中部位从轮廓线附近转移到距轮廓线约5.0 m的围岩深部,后者通过爆破卸压作用在掌子面前方产生一定延伸范围的松弛区,可有效释放掌子面处的集中应力。进一步基于拉森斯岩爆判别法对比两方案的岩爆防治效果表明原来可能发生强烈岩爆的部位,采用爆破卸压释放应力后岩爆烈度等级均降低为弱岩爆,掌子面发生岩爆的可能性也显著降低。现场试验验证研究进一步论证了基于爆破卸压理论的快速应力释放方法来防治岩爆的可行性和有效性,并深入分析了两种爆破卸压方案对强岩爆防治的优势。综合研究成果并结合现场实际应用情况,提出了锦屏二级引水隧洞工程岩爆防治的综合措施,为强岩爆环境下爆破开挖设计和施工提供方法与理论支撑。

The strong rockburst disaster in deep tunnels is a difficult issue for the safety of excavation and the efficient application. The design of scientific blasting excavation has become an important technical means for the effective control of strong rockburst disasters. This paper conducts a aseries of numerical simulation and field tests involving the efficiency of the destressing blasting control on the strong rockburst disasters, based on the prevention and the control of frequent strong rockburst disasters with the increase of buried depth and in-situ stresses at diversion tunnels at Jinping Ⅱ hydropower station. The two destressing blasting schemes are demonstrated by numerical simulation. The one is to use twin-row inclined radial drillings in rock walls and the other is to apply vertical advance boreholes on tunnel faces. The results indicate that the relaxation zones appear at the left side wall blasting holes, the central part of the vault, the right side haunch and the spandrel blasting holes, after performing the scheme one. As for the method two, the extended range of relaxation zones occur in front of the tunnel faces by means of destressing blasting and release concentrated stress on tunnel faces. Based on the comparison of the Russenses Rockburst Discrimination Law, the two methods play an important role in the rockburst prevention and control effect. The intensity of rockburst after destressing blasting is reduced and occurs a strong rockburst, such as the left side of the wall between the bottom to the haunch, the right side of the wall ranging from the lower haunch to the vault, the left side of the spandrel and the right side of the bottom wall. Furthermore, the possibility of the rockburst occurrence on the face is also significantly reduced. Field test verification further demonstrates the feasibility and effectiveness of the rapidly released stress based on blasting pressure relief theory to prevent and control rockburst. In addition, the field tests analyze the advantages of the two schemes on blasting relief for preventing and controlling strong rockburst. Based on the comprehensive research and the field application, this paper proposes several rockburst prevention and control measures at diversion tunnels in Jinping Ⅱ hydropower station, which is benefit for the design and construction of blasting excavation in strong rockburst.