锦屏一级水电站左岸边坡深部裂缝成因初探

 对锦屏一级水电站边坡工程地质条件、坝址区实测地应力分布及左岸深部裂缝发育规律进行全面分析，采用UDEC和3DEC离散元程序模拟锦屏一级水电站河谷的演化发展，对河谷边坡不同演化阶段应力场的变化规律及变形与卸荷分带规律进行深入分析。根据数值模拟结果并结合河谷边坡变形及地应力现状特征，认为锦屏一级水电站左岸发育的深部裂缝是在河谷地质结构上软下硬、地层反倾、上部开阔下部狭窄、下蚀迅速和区域高应力背景的特定条件下，在河谷下切至1 830～1 730 m高程阶段造成边坡1 700～1 850 m高程范围的局部应力集中到超过岩体强度而产生岩体屈服破坏的结果。从工程地质定性的角度分析，目前左岸发育的深部裂缝对边坡稳定性的影响有别于区域构造断层，其对工程边坡的影响是有限的、局部的，工程中切实保护河谷1 680 m高程以下岩体是控制深部裂缝进一步发展及保证边坡稳定的基本原则。

PRIMARY RESEARCH ON MECHANISM OF DEEP FRACTURES FORMATION IN LEFT BANK OF JINPING FIRST STAGE HYDROPOWER STATION

At first，the slope geological conditions as well as dam site geostress and deep fractures in the left bank of Jinping first stage hydropower station have been investigated. Then the evolvement and development of Jinping first stage hydropower station valley are simulated by using distinct element codes UDEC and 3DEC；and stress field，deformation and unloading zone distribution of valley are comprehensively analysed. Based on the simulation results and the deformation of present slope，it is considered that the deep fractures at elevation 1 700– 1 850 m at the left bank of Jinping first stage hydropower station are the yield results due to valley erosion to elevation 1 830–1 730 m at the special geological structures，such as soft upside rock and hard underside rock，the dip direction of rock reverse against slope，wide upside and strait underside of valley and the high regional tectonic stress of Jinping first stage hydropower station valley. From the view of engineering geology，the effect of deep fractures at the left bank on the slope stability is different from tectonic faults，and its influence is limited and local. Be sure not to disturb rock masses under elevation 1 680 m is the best way to keep engineering slope safe and to prevent the deep fractures from developing.