特高坝地基深大断裂活动性与筑坝工程地质问题研究

DEEP FAULT ACTIVITY OF ESPECIALLY HIGH DAM FOUNDATION AND GEOLOGICAL ISSUES OF DAM ENGINEERING

某拟建水电站为高坝大库,挡水建筑物系200m级碾压混凝土重力坝,系我国在境外投资建设的重大能源项目之一. 该水电站位于一条区域性的深大断裂（ F4断裂）上,该断裂的活动性以及涉及的筑坝技术可行性为本工程的重大技术课题,关乎水电站成立与否的关键.为此开展了区域地震地质调查、物探、钻探、硐探、断裂物质测龄以及岩土物理力学性质现场和室 内测试等大量工作,研究表明（ 1）该断裂地震活动微弱,最新活动年龄14. 2万-79. 8万年,是一条晚更新世以来不活动的断裂,为非活动断层;（ 2）F4断裂对水坝建设存在影响的部位主要为碎裂岩带和F4-1、F4-2断层,其中微新碎裂岩多为Ⅲ1B类岩体,仅F4-2断层下盘影响带内的碎裂岩岩体为Ⅳ1B类岩体, F4-1、F4-2断层带工程性质差,为Ⅴ类岩体,是坝基最软弱的部位;（ 3） 在F4断裂带上筑坝,建库后诱发构造型水库地震的可能性小,存在的主要工程地质问题为坝基变形和渗漏、渗透稳定问题,可 通过适当深挖,并结合回填混凝土塞、固结灌浆、加深加密帷幕孔以及增加帷幕排数等工程措施予以处理.因此,F4断裂带上 可以兴建水电站工程,筑坝技术可行.结果可为该水电站设计、施工提供技术依据,为类似工程提供技术参考.

This paper examines a planned hydropower station that is one of the important energy projects in overseas invested by China. It has a reservoir with high dam. Its water retaining structure is a roller-compacted concrete gravity dam of 200m high. The dam is located at a regional deep fault （ F4 ） . Activities of fault and feasibility of damming technology, as an important technical issue,is key to the establishment of hydropower station. Thus, a lot of work, including regional seismic geological investigation, geophysical prospecting, drilling, exploratory adit, fault age, field and indoor tests for rock and soil physical and mechanical properties, has been conducted. Results show that： （1） Seismic activities in this fault are weak and the latest one is from 0. 142million to 0. 798million years ago. The fault is inactive since late Pleistocene. （2） Cataclastic rock belt and the faults F44 and F4 2 have the most influence on the dam. The fresh cataclastic rock mainly is the Ⅲ 1B class rock. The Ⅳ1B class rock only exists in F4 footwall. Faults F4-1 and F4- 2, which is composed of the Ⅴ class rock, have bad engineering properties, and are the most weak part of dam foundation ; （ 3 ） The possibility of building the dam at fault F4 to induce stereotype reservoir earthquake is less. The main engineering geological problem is deformation and seepage in dam foundation. Seepage stability can be dealt with through appropriate engineering measures such as deep digging and combining with backfilling concrete plug, consolidation grouting, deepening encryption and increasing the curtain row number. With results mentioned above all, an conclusion can be made that conducting hydropower projects on the fault F4 zone is viable in technical way. The results can only provide technical basis for hydropower station design and construction, but also technical reference for similar projects.