坝基岩体开挖卸荷与分带研究——以小湾水电站坝基岩体开挖为例

 小湾坝基开挖引起了一系列岩体卸荷变形破坏现象，包括岩体中已有结构面的回弹松动与剪切错动，以及完整岩体的岩爆拱裂、薄板状破裂等新生破裂。开挖中岩体的新生破裂面在空间分布上有如下特点：破裂面产状与开挖面具有较好的一致性；在深度分布上，开挖卸荷破裂面相对集中在开挖面之下4～6 m的深度以上。岩体的卸荷变形破坏导致了岩体完整性的显著降低，但卸荷松动过程的主体部分多在几个月内完结。无论是岩体开挖卸荷还是河流天然切割卸荷都是一个能量释放过程，并且卸荷变形破坏具有显著的空间分布规律，因此采用能量方法研究岩体的卸荷分带是合适的。给出了岩体卸荷分带的应变能方法，小湾水电站的实际应用表明该方法是可行的、有效的。

RESEARCH ON UNLOADING AND ZONATION OF ROCK MASS DAM FOUNDATION EXCAVATION-A CASE STUDY OF XIAOWAN HYDROPOWER STATION

The excavation has induced a series of unloading deformations and failure phenomena of rock mass including loosening and shearing deformation of existing discontinuities，and outburst and flaky failure of intact rock. The attitudes of the new failure planes are nearly parallel to the excavation surface；and the planes mostly are distributed within the depth of 4–6 m. The unloading deformation and failure have led to a notable decrease of integrality of rock mass，however，the main courses of relaxation are completed in several months. Since the excavation unloading is actually an energy release course whether it is provoked by excavation of rock mass or natural cutting of rivers. There is a clear distribution regulation for the deformation and failure phenomena，so it is suitable for investigating the unloading zones by the energy analysis method. A strain energy method for unloading zonation is presented，and the application of Xiaowan Hydropower Station has confirmed its feasibility and efficiency.