高地应力条件下地下厂房洞室群围岩的变形破坏特征及对策研究

摘要

Underground powerhouse caverns of Guandi Hydropower Station have the characteristics of high geostress and widely distributed discontinuities in hard surrounding rocks. Based on the characteristics analysis of geostress, rock mass structure and the conclusions derived from the monitored deformation data and the three-dimensional numerical simulation results, the deformation and failure characteristics of rock mass are summarized. The countermeasures for general layout design, excavation support design, construction of powerhouse caverns under high geostress condition are proposed based on systematical summarization. Following proposals are made for high geostress condition, such as the direction of the maximum principal geostress and the main discontinuities in the surrounding rock should be taken into account when the longitudinal axis of the chamber is chosen; adopting larger distance between the main chambers; adopting larger ratio of height to span of the top arch; adopting reasonable methods and sequence for excavation; improving the strength grade of shotcrete; delaying concreting the rock wall crane beam and the lining of busbar tunnels; determining reasonable initial prestress of the anchor cables. Also, for surrounding rock where rockburst is likely to take place, it is suggested that the initial steel fiber shotcrete with a thickness of 50 to 60 mm should be sprayed firstly; and then to install the systematical anchor bolts; finally to implement the designed remaining shotcrete with wire mesh. The above-mentioned proposals provide great guiding significances and application values for design and construction of similar underground powerhouse caverns under high geostress condition.%依据官地水电站大型地下厂房洞室群地应力高、围岩坚硬、结构面发育等特点,在地应力特征、围岩结构特征分析的基础上,结合围岩变形监测成果和三维数值仿真分析成果,对洞室围岩变形破坏特征进行归纳总结,并系统提出高地应力条件下地下厂房洞室群的布置设计、开挖支护设计和施工对策.建议高地应力条件下,洞室纵轴线的选择应兼顾最大主应力方位和围岩主要结构面、采用较大的洞室间距和较大的顶拱矢跨比、采用合理的开挖方式和开挖顺序、适当提高喷混凝土强度等级、延时浇筑岩壁吊车梁和母线洞衬砌、合理确定锚索张拉力锁定值,对具备岩爆条件的洞室围岩先初喷50～60 mm厚的钢纤维混凝土后再实施系统锚杆和挂网喷混凝土层到设计厚度等.上述建议对于高地应力条件下类似地下厂房洞室群的设计与施工具有重要的指导意义和应用价值.