长江技术经济

为研究大断面引水隧洞的围岩稳定性问题，以巴拉水电站跨断层大断面引水隧洞为研究对象，通过现场试验、数值模拟研究了原支护状态下围岩的失稳变形，得出了大断面引水隧洞的围岩变形机理，结合室内试验验证了NPR锚索的超常力学性能。结果表明：受断层破碎带的影响，研究区域的岩体节理裂隙较为发育，岩体完整性较差，隧洞围岩存在变形、坍塌的风险；采用普通锚杆与I20a钢拱架耦合的支护方案，隧洞的最大位移仍然达到了约391 mm，原支护措施无法有效约束隧洞围岩的变形；NPR锚索的恒阻力约为250～350 kN，具有良好的恒阻特性，可应用于软岩大变形隧洞的围岩支护。研究成果可为其他软岩隧洞的支护提供依据。

To investigate the stability of the surrounding rock in large-section diversion tunnels,this study takes the cross-fault large-section diversion tunnel of the Bala Hydropower Station as a case study.Field investigations and numerical simulations were conducted to elucidate the instability and deformation mechanisms of the surrounding rock under the original support conditions.Laboratory tests were carried out to verify the exceptional mechanical performance of the NPR anchor cable.The research findings are as follows:(1) Due to the presence of a fault-fracture zone,the rock mass in the study area was intensively jointed and fissured with markedly poor integrity,posing deformation and collapse risks to the surrounding rock.(2) Even with a support system combining ordinary rock bolts and I20a steel sets,the maximum displacement of the tunnel reached 391 mm,indicating that the original support was ineffective in constraining the deformation of the surrounding rock.(3) The constant resistance value of the NPR anchor cable ranged from 250 to 350 kN,demonstrating excellent constant resistance characteristics and making it suitable for supporting large-deformation soft rock tunnels.The results provide a reference for the support design of other soft rock tunnels.