明潭地下廠房設計與施工之大地工程問題

Geotechnical Problems Concerning the Design and Construction of Mingtan Underground Powerhouse

高呈毅(C. Y. Kao)

《鑛冶：中國鑛冶工程學會會刊》 34卷2期 (1990/06) Pp. 17-26

https://doi.org/10.30069/MM.199006_34(2).0002

摘要

明潭地下廠房之地質由外車埕砂岩組成，岩性之變化甚大，其主要之地質特徵為平行層面之斷層及泥縫特別發達。不良之地質條件使得原設計之廠房佈置因而修正，並導致在主體開挖前預先在廠房頂拱施作層縫處理（Seam Treatment）以改良岩質；及裝設鋼腱預錨（Pre-reinforcement）以增加頂拱岩盤弱面之抗剪強度。廠房之支撑更首次在國内使用鋼纖維噴凝土（Steel Fiber Reinforced Shotcrete），配合岩釘（Rock Bolt）與預力鋼腱（Prestressed Tendon），組成岩盤柔性之支撑工。由於臺灣位處環太平洋地震頻繁帶，地震設計之理念亦被融入廠房之支撑設計中，以因應地震可能造成之影響。此外，在廠房開挖期間，吾人亦利用監測儀器所得之資料，採用數值分析法（FLAC），隨開挖之進行，適時進行反算分析（Back Analysis），以確保廠房之穩定。

並列摘要

The geology of Ming tan powerhouse is composed of Waichecheng sandstone, in which the quality of rock mass varies greatly. The most paramount geological feature is the occurrence of bedding parallel faults and clay seams which have led to the reorientation of the cavern axis. Seam treatment and pre-reinforcement were aIso conducted to improve the rock quality and increase the shear resistance of the rock mass in cavern roof before the commencement of the cavern excavation. For the first time in Taiwan, steel fiber reinforced shotcrete was used in combination with rock bolt and prestressed tendon to form a flexible support for the rock mass in cavern area. Taiwan is situated in the Circum-Pacific mobile belt, therefore seismic design concept was applied in the support design to account for the impact earthquake may cause. Back analysis utilizing monitoring results were also conducted during excavation to make sure the cavern stability was acceptable.