厄瓜多尔CCS水电站引水隧洞TBM选型及工程地质问题与对策

Problems on TBM Section and Engineering Geological Conditions and Countermeasures in Construction of Headrace Tunnel at CCS Hydropower Station in Ecuador

厄瓜多尔CCS水电站引水隧洞全长24.8 km,开挖洞径9.11 m,隧洞开挖拟采用TBM法。隧洞沿线地质构造较复杂,断层发育,水文地质条件不良。对开敞式、单护盾及双护盾3种类型TBM技术特点和地质适应范围进行了细致分析,同时结合CCS水电站引水隧洞的工程地质条件和存在的工程地质问题,并参照国内外已有的TBM工程实践,决定CCS水电站引水隧洞施工选用双护盾TBM。围岩分类和超前地质预报是CCS水电站引水隧洞TBM施工过程的两项重要地质工作。通过岩石现场回弹测试、掌子面及洞壁围岩局部观测、岩渣分析、掘进参数分析、地下水流量观测及测试等方法获取围岩分类指标,建立围岩分类标准,并确定合适的管片支护。通过地质分析、物探法、超前钻探的综合预报方法,查明掌子面前方的不良地质条件,为TBM的顺利掘进提供保证。针对施工过程中出现的断层破碎带塌方、涌水、砂岩砂化等工程地质问题,提出有效的处理措施。施工实践表明:CCS水电站引水隧洞选用双护盾TBM是成功的。

The headrace tunnel of CCS hydropower station in Ecuador is 24. 8km in length and 9. 11 m in diameter, which is suitable for tunnel excavating by TBM method. The geological structure along the tunnel is complicated with fault development and adverse hydrologic geology conditions. In this paper, the technical characteristics and geological a-daptive ranges of the open-type TBM,single - shield TBM and double-shield TBM are analyzed in detail. Combined with the engineering geological conditions of the project and their existential questions, double-shield TBM is selected for tun-nel construction after an assessment of existing TBM engineering practices. Rock classification and advanced geological prediction were two important geological work in TBM tunnel construction process. The methods such as rock rebound tes- ting,surrounding and tunnel face local observation, rock gravel analysis, tunneling parameters analysis, and groundwater flow observation and testing are used to establish classification indices and standards for surrounding rocks, and confirm appropriate segment lining. Adverse geological conditions in the tunnel face are detected out by the comprehensive predic-tion method of geological analysis,geophysical exploration, and advanced drilling,which provides a guarantee for the pro-pitiousness driving of TBM. Effective measures are proposed in the construction process for the engineering geological problems like the fault fracture zone collapse,water gushing and sandification. Construction practice shows that it is tri-umphant toapply double-shield TBM into the headrace tunnel of CCS hydropower station.