英文篇名
A Study on Support Design and Construction of Large Cavern Excavations in Fractured Rock Masses
作者
劉弘祥、廖俊逸、林孟德、李錦浚
關鍵字
破碎岩盤、大型洞室、鋼纖維噴凝土、岩釘、預力鋼腱
摘要
本文探討之大型洞室位於台灣中部山區大甲溪右岸約50m之山腹內,開挖尺寸約長49.0m,寬19.6m、高18.0m,最大岩覆約70m。根據地質調查結果顯示,本區域岩盤主要以板岩為主,有2~3組節理發育,岩盤破碎,岩心品質(RQD)多小於20且局部夾有剪裂破碎帶,整體而言,依CSIR岩盤分類法應屬IV~V類岩盤。洞室之支撐設計採挪威岩盤品質(Q值)法進行,計算開挖後所需之支撐壓力,據以進行支撐工之配置,支撐材料包括鋼纖維噴凝土、岩釘、預力鋼腱、頂拱鋼支保及臨時鋼支柱等,頂拱無鋼筋混凝土襯砌,僅安裝鋁質天花板作為裝飾。為減少大型洞室開挖演生大量變位,必須先由頂拱分區開挖及支撐,再逐階分區降挖及支撐。為克服破碎岩盤造成支撐材料錨碇力不足問題,必須利用預力鋼腱進行預灌及地盤改良。由於採用安全監測及回饋分析等措施,本大型洞室得以順利完工。
英文摘要
The large cavern was located at the right bank of Tachia River, which was into hillside about 50m. The dimensions of cavern was 49.0m in length, 19.6m in width, 18.0m in height, and the overburden shown about 70m. According to geological survey, the regional slate bedrock develop 2~3 sets of joint. The rock quality designation (RQD) values were mostly less than 20, and existing local fracture zone. Overall, the rock mass classification of CSIR should be IV~V in excavation area. Based on NGI-Q method, the design of support system consists of the steel fiber reinforced shotcrete, rock bolts, tendons and temporary steel supports. There wasn’t reinforced concrete lining on crown. In order to reduce the deformation, the excavation and support sequence must start from the crown partition, and then gradually to bench partition. To overcome poor anchorage strength condition caused by fractured rock masses, the ground treatment must be taken by the use of pre-grout tendon. As a result of the measures of safety monitoring and feedback analysis, the large cavern was completed smoothly.