复杂层状建基岩体可利用性及开挖深度优化研究

建基岩体的可利用性及开挖深度关系到水电站工程的可行性、合理性及经济性等，是技施阶段重要研究内容之一。基于对坝基不同岩性及其组合的岩石力学特性试验、岩层厚度、RQD值、波速测试及配套的现场大型变形试验等，研究了复杂层状建基岩体的结构特征和质量标准，并基于岩体波速建立岩体结构、岩体质量及变形参数的预测评价模型，确定了复杂层状岩体的可利用性标准，并对开挖深度进行了优化研究。结果表明：在砂岩类占比约60%的整个坝基岩体中，微新及以下复杂层状砂板岩以坚硬岩为主，且原位状态下岩体层面效应基本消失，完整性大幅提高；岩体波速与岩体结构、岩体质量及变形参数间具有很好的对应性；基于岩体波速建立了建基岩体利用标准，并将河床建基面开挖深度整体抬高约10 m，减少了岩基开挖和混凝土浇筑量并缩短了工期。

Study on availability of complex layered foundation rock of dams and excavation depth optimization

The availability and excavation depth of dam foundation rock, which are of important research issues in the stage of technologically design and detailed constructional drawing, are related to the feasibility, rationality and economy of hydropower projects. Based on mechanical properties of different lithologies and their combinations, such as rock thickness, RQD value, wave velocity and large-scale in-situ deformation tests, we study the structural features and quality standards of complex layered foundation. Based on the wave velocity of rock, we established an evaluation model that could forecast structure, quality and deformation parameters of rock mass. Besides, we have also determined the availability standards of complex layered rock and conducted a research to optimize the depth of excavation. The results show that for the entire dam base rock mass of which sandstone accounting for about 60%, slightly fresh or older complex layered sand-slate are characterized as hard rock; the level effect of rock disappears basically and its integrity is greatly improved. The wave velocity of rock is well corresponded to its structure, quality and deformation parameters. Based on the wave velocity of rock, we propose the availability standards of structural foundation rock. By these measures, the excavation depth of the riverbed structural foundation is reduced by 10 meters, which reduces excavation volume of rock foundation and quantity of concrete pouring and shortens the construction period.