大渡河金川水电站坝区节理构造及工程稳定性影响

Joint structure in the dam area of the Jinchuan Hydropower Station on the Dadu River and its influence of project stability

运用野外观察分析和构造解析方法,遵循共轭节理配套分期原则对大渡河金川坝区发育的节理构造进行逐步分析研究,可将该区发育的NE向、NEE向,NEE向、SW向,倾向SW、倾向NE,倾向SEE和倾向NWW的节理构成4套共轭节理,分别属于区域北西向和南北向构造的组成。据此推出该区节理的形成、发育先后受到印支—燕山期北西向构造应力场、喜马拉雅期南北向构造应力场的影响和制约。该区岩层倾向南西,第一期节理与岩层面倾向相反;第二期节理与层面倾向近乎一致,起到主要控制作用。在工程建设中,两期节理共同作用切割岩体,前者易于破碎岩石,后者则易于形成滑坡。两期节理的研究对工程的稳定性研究具有重要的意义。

Through field observations and structural analysis and in light of the principle of classifying the joints according to their strikes and dips into conjugate joint sets and determining their phases, the joint structure developed in the Jinchuan dam area of the Dadu River was analyzed and studied. The authors classified the NE-, NW-, ENE- and ENE-striking and SW-, NE-, ESE- and WNW-dipping into four sets of conjugate joints, belonging to the regional NW- and N-S-trending structures respectively. According to this conclusion, the authors deduce that the formation and development of the joints in the area were affected and constrained by the regional Indosinian-Yanshanian NW-trending structural stress field and Himalayan N-S-trending structural stress field. The strata in the area dip SW, and the joints of the first phase dip in the opposite direction of the dip of the bedding of the strata, while the joints of the second phase dip in almost the same direction as the dip of the bedding. The joints of the second phase play the principal role in controlling the structural movement. In the civil engineering construction, joints of the two phases combine to cut the rock masses. The former is prone to crush rocks, while the latter is prone to form landslides. The study of the two phases of joints has great significance for the study of the engineering stability in the dam area of the Jinchuan hydropower station.