锦屏二级水电站地下厂房下游拱肩开裂与中隔墙锚索破坏原因分析及处理措施

Analysis and repair of downstream spandrel crack and middle partition wall anchorage cable failure for underground powerhouse of Jinping Ⅱ Hydropower Project

针对锦屏二级水电站地下厂房开挖支护中后期,下游拱肩开裂、外鼓、剥落及混凝土浇筑期间中隔墙锚索破坏问题,分析其原因,认为是与洞轴线成小夹角的层状陡倾角岩体受该部位强烈集中的高地应力影响和中隔墙岩体三向卸荷变形影响有关。为此,对地下厂房和主变洞下游拱肩开裂部位采用表层、浅层和深层喷锚支护措施进行综合处理,对中隔墙岩体进行低压固结灌浆。实施后,效果好,有效地保证了围岩稳定与厂房安全。

During construction of underground powerhouse of Jinping II Hydropower Project, downstream spandrel crack, outward bulging and peeling were seen in the middle and late periods of excavation and support, middle partition wall anchorage cable failure was seen during concreting. The authors analyzed the causes, including the layered steep dip rock mass at small angle to axis of underground chamber is subject to concentrated high geostress; and the rock mass at middle partition wall is affected by three-dimensional unloading deformation. Therefore, surface, shallow and deep shotcrete-boh support was adopted to repair the downstream spandrel crack; rock mass at middle partition wall was repaired by low pressure consolidation grouting. The repair measures render good effects and ensure the stability of surrounding rock and powerhouse safety.