白鹤滩水电站坝址区岸坡深部发育大量既非构造成因、又区别于常规卸荷裂隙的深部破裂,有关此类特殊地质现象的成因机制及其对工程的影响已成为水电站建设亟需解决的问题.以深部破裂现场精细描述为基础,总结深部破裂基本特征与发育分布规律,结合构造演化、河谷演化及浅生改造理论,辅以现场地应力测试及测年成果,采用地质过程机制分析方法,还原深部破裂形成演化过程,分析其成因机制.研究结果表明:坝址区深部破裂是伴随河谷快速下切过程中形成的浅生结构,其方向具有双向性,且表现出明显的张性特征,分布具有集中性,以左岸约0.5倍坡高、硐深约l00m附近最为发育,均位于控制性错动带上盘,处于岸坡应力波动带内部,属构造应力场与斜坡应力场共同作用下的复合应力场.深部破裂形成的驱动力是伴随河谷下切过程中岸坡岩体内出现的残余拉应力,伴随应变能的释放过程产生,其形成年代大致对应于Ⅲ级阶地形成初期,即Qp2晚期-Qp早期阶段.%There were a large number of deep fractures within the slope of the Baihetan hydropower station dam area, which was neither tectonic origin nor different from conventional unloading fractures,the formation mechanism of such special geological phenomena and their impact on engineering construction of hydropower stations had become a problem that needed to solve. The characteristics and distribution pattern of deep fractures was summarized on the basis of detailed description of deep fractures and the formation mechanism was analyzed by combining with tectonic evolution, valley evolution of canyon and the theory of near surface action and by the result of in situ stress testing and dating, using the mechanism analysis of geological processes. The results show that the deep fractures is epigenetic structure with NW and NE orientation, tensile characteristics, concentration distribution,location above the dislocation belt and is in the stress fluctuation zone of slope. The primary reason of deep fractures formation is strain energy release and residual tensile stress caused by difference resilience. Formation age of deep fractures is after Ⅲ terraces appearance,namely Late Qp2 ˉˉEarly Qp stages.
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