Abstract: Based on the the overstressing on rock support system in the excavation of tailwater surge chamber of Yangfanggou hydropower station, combined with on-site geology, support scheme and monitoring scheme, the dynamic feedback analysis model is established. Analysis results show that the main reason for the overstressing on rock support system is, on one hand, local unloading and relaxation caused by the exposure of dominant joints with middle and high angles on the side wall and along the chamber. On the other hand, the construction blasting exerts great influence on the bolt stress as the monitoring instruments are close to the excavation boundary. By analysis and according supplementary support, the deformation and bolt stress of the area tend to converge. The evaluation method can be used to analyze the the overstressing on rock support system.

Key words: tailwater surge chamber, dynamic feedback analysis, rock bolt, over-limit

摘要： 依托杨房沟水电站尾水调压室下卧过程中出现的支护受力超限问题，充分结合现场实际地质信息、实际支护方案、监测方案建立动态反馈分析模型，分析发现锚杆受力超限一方面主要因为开挖造成尾调室边墙顺洞向中陡倾角优势节理揭露，形成区域开挖卸荷松弛问题；另一方面由于监测仪器布置距开挖分界层较近，导致施工爆破对锚杆受力影响较大。经分析及补强支护后，该区域变形及支护受力趋于收敛。该评价方法可为地下洞室围岩支护超限提供分析思路。

关键词: 尾水调压室, 动态反馈分析, 锚杆, 超限