尼泊尔喜马拉雅地区塔玛科什3级水电工程--穿越软弱构造片岩修建隧洞所面临的挑战  

Tunnelling Challenges Through Weak Tectonised Schist in Nepal——Himalaya Tamakoshi 3 Hydroelectric Project

作　　者：Subas Chandra Sunuwar Sandip Shah Ashish Subedi Muna Sharma 

机构地区：[1]SN Power Ltd.

出　　处：《现代隧道技术》2013年第1期1-7,15,共8页Modern Tunnelling Technology

摘　　要：由于尼泊尔喜马拉雅地区岩石强度较低,水平应力较高,因此在该软弱构造片岩带中开挖隧洞具有较大的挑战性。文章主要阐述装机容量为650 kW的塔玛科什3级水电工程17km长大跨度隧洞和大型地下发电厂房(这两项工程计划穿越夹杂有软弱构造片岩带的坚硬眼球状片麻岩区域)所面临的重大技术挑战。穿过片岩带开挖的隧洞长度约占总长的15%,由于此岩层带岩石强度较低,具有剪切特性和渗流现象,且水平应力较高,围岩挤压和隧洞塌方都是可预期的问题,因此该工程地下开挖主要关注的问题是大尺寸隧洞的可施工性和工期。为了解决可预期问题,进行了更进一步的研究,主要集中在隧洞最大可建尺寸、方位、减少围岩挤压的开挖方法,以及地下发电厂房稳定性和合理岩石支护设计上。研究发现,在构造片岩带中可施工的全断面隧洞最大尺寸可达9m,为改进的马蹄形(有弧形仰拱)。通过对隧洞三种不同方位方案(即正交、斜交、平行)的分析发现,与叶理面正交的方案最佳,可减少围岩挤压近50%。Tunnelling through weak tectonised schist bands is a challenge in Nepal Himalaya due to low strength rock and high horizontal stress condition. In this paper, a tunnelling challenge is considered from 650MW Tamakoshi-3 Hydroelectric Project where a large span, 17kin long tunnel and large underground power house are pro- posed through strong augen gneiss with embedded weak teetonised schist bands. These bands, aligned parallel to the foliation plane （20°-30°1000° -010° ）, are characterised by weak （〈ISMPa）, crenulated, sheared, chlorite-sericite- taleose schist with clay gouge with thickness varying from a few centimetres to a maximum of 60m. About 15% of the tunnel length has to be excavated through the schist bands. Rock squeezing and tunnel collapse are expected chal- lenges when tunnelling through such bands due to low strength, sheared nature, seepage and high horizontal stress. Therefore, underground excavation for the Project raised concern about large size tunnel construetability and longer construction time.

关 键 词：水工隧洞 软弱构造带 数值模拟 最佳设计方案 

分 类 号：U452.27[建筑科学—桥梁与隧道工程]