白鹤滩水电站地下厂房错动带围岩稳定性控制方法研究

软弱错动带C2、C4分别加剧了白鹤滩两岸主厂房围岩的变形破坏风险和程度,为研究错动带影响机制和特点,制定针对性控制措施,依据现场破坏现象、监测数据,结合理论分析和数值反馈方法考察左厂边墙揭露C2、右厂顶拱揭露C4 2种条件下的围岩开挖力学响应特点和破坏机制,提出错动带不利影响控制措施,并评价工程措施的有效性及其相应条件下的厂房稳定条件。研究结果表明： 1）由主洞+支洞联合抗剪、交叉锁口构成的组合措施,可有效控制沿C2发生的剪切变形对左岸主厂房边墙松弛变形的加剧效应; 2）错动带C4在构造运动中形成局部地层应力异常并与开挖二次应力叠加作用,导致右岸主厂房顶拱层高应力破坏风险增加; 3）强化表面支护+深部加固组合措施可对C4影响部位的浅层和深部围岩综合起到“维持”和“加固”作用。系统支护和错动带组合控制措施可有效保证主厂房整体稳定性。

Surrounding Rock Stability Control Methods in ShearBands of Underground Powerhouse of Baihetan Hydropower Station

The shear bands C2 and C4 aggravate the risk ofdeformation and failure of the surrounding rock of Baihetan main powerhouses.As a result, corresponding control measures must be developed. According tofield failure phenomena and monitoring data, the response characteristics andfailure mechanism of surrounding rock under the conditions of C2 exposing atthe sidewall of the left plant and C4 exposing at the roof arch of the rightplant are investigated using theoretical analysis and numerical feedbackmethods. Some control measures for the adverse impact of the shear band areproposed, and corresponding evaluations of the effectiveness of measures takenare conducted. The research results show the following: (1) The combinationmeasures of main shear resistance tunnel and branch tunnel combined with crosslock can effectively control the aggravating effect of shear deformation alongwith C2 on the relaxation deformation of the sidewall of the main powerhouse atthe left bank. (2) The superposition of abnormal stress locally induced by C4during tectonic movement and excavation secondary stress increases the risk ofstress induced damage to the roof arch layer of the right bank′s main powerhouse. (3) Surface support and deep reinforcementmeasures combined can provide maintenance andreinforcement to the shallow and deep surrounding rock affected byC4. The results show that shear band system support and control measures canensure the overall stability of the main powerhouse.