地質改良與新奧工法

Ground Improvement for NATM Tunneling in Soft Ground

黃南輝(R. N. Hwang) ； 王復國(F. G. Wang) ； 鄭國雄(K. C. Cheng) ； 陳奕耿(Y. K. Chen)

《地工技術》 78期 (2000/04) Pp. 87-102

https://doi.org/10.30140/SG.200004.0006

摘要

台北都會區捷運系統南港線CN256B標之隧道係位於忠孝東路與基隆路口下方，西側銜接CN256標潛盾隧道，穿越基隆路車行地下道下方後，往東與CN257標之市政府站（BL13）西端連續壁銜接，上下行隧道全長共約98m，開挖直徑為6.4m，中心深度約於地表下13.5m，兩隧道中心距約20m，採新奧工法施工。因所處地層多屬軟弱粘土層，故以地盤改良為穩定地層輔助工法。本文中依序說明基地地層與地下水壓狀況、施工概況、地盤改良、隧道開挖及安全監測系統等。由觀測資料得知南側（上行）隧道開挖構築期間，因開挖區地層之地盤改良效果佳，施工引致之最終地面沉陷僅約30mm，北側（下行）隧道則因該區地下管線縱橫密佈，地盤改良作業施作不易，致其地盤改良效果不佳，於鏡面破除及隧道開挖初期，地層曾一度有明顯沉陷情形，頂拱及支堡基腳亦相繼有過量下陷，隧道有淨空不足現象發生。後於原支堡間各增設一對臨時性支堡補強，並在開挖面前方上緣，及兩側支堡腳底部打設鋼管加勁，以阻隔滑動面及提高支堡支承力。淨空不足部份則於支堡間依序進行刻槽、架設支堡、噴漿而後再挖除侵入部份，經採上述補強措施後，本隧道得以安全、順利完成開挖及內襯砌構築作業，並且地面最大沉陷量控制在240mm以內。

關鍵字

隧道 ； 新奧工法 ； 地盤改良 ； 監測系統 ； 頂拱 ； 支堡 ； 沉陷

並列摘要

A section of twin tunnels, with a diameter of 6.4m and a total length of 98m, in the Nankang Line of the Taipei Rapid Transit Systems was constructed using the NATM method. The subsoils in which the tunnels are buried are young sediments and are very weak in strength. Ground treatment was necessary for maintaining the face stability during tunneling. Jet grouting was applied and the performance of the two tunnels was quite different because of the different conditions encountered. For the up-track tunnel, ground treatment was successful and settlements were well within 30mm. On the other hand, ground settlements above the down-track tunnel reached 240mm because of the poor treatment due to the presence of utilities. Excess ground movements called for additional temporary supports and the use of soil nails. With considerable efforts, the tunnel was completed without accidents.

並列關鍵字

tunnel ； lining ； NATM ； soil improvement ； instrumentation ； temporary support ； settlement