新莊線頭前庄站人行地下道管幕推進工法

(文圖/李蔚 英譯/沈淑華)

管幕機頭及油壓千斤頂
管幕機頭及油壓千斤頂
預鑄箱涵內部開挖
預鑄箱涵內部開挖

捷運新莊線頭前庄站穿越新莊市思源路人行地下道工程因位於新莊區中正路(省道)、思源路口與大漢橋上、下橋處,位處連接三重、新莊、板橋等地區之交通樞紐;且地下管線眾多,即使花費上億元經費,亦無法遷移,且工區腹地狹小,無法以原設計之明挖覆蓋方式封閉道路進行施工,僅能利用人行道、道路外側混合車道及大漢橋下之橋墩間的有限空間進行,不得不變更改採管幕與預鑄四角箱涵推進工法進行。

本案穿越新莊區思源路大漢橋西側往板橋方向路段,距離14.2 公尺,覆土深度5.05 公尺,採先推進42 支管幕形成口字型外撐後,再推進四角預鑄鋼筋混凝土箱涵共15 節,推進完成後再與明挖覆蓋段場鑄之人行地下道接合。

管幕施工主要是利用管幕機將加工過之鋼管穿過土層向預定位置推進,鋼管與鋼管之間利用特製卡榫互相結合,鋼管呈連續排列形成管幕。管幕施工採「一次工法」,即管幕機頭與鋼管同時推進一次施工完成,鋼管推進完成後於鋼管接頭處進行藥液止水灌漿。管幕全部完成後於鋼管內部灌注水泥砂漿。

由本工程可知在地窄人稠、交通樞紐、地下複雜管線無法遷移、施工空間有限等不利條件下,採用管幕及預鑄箱涵推進工法,將是較經濟且可行的方式。管幕工法因接榫多,所以工作井的鏡面、封底、介面等止水灌漿須特別要求,且在鏡面破除前須進行試水檢測,以維施工安全。在軟弱地質中施作管幕及預鑄箱涵推進,須注意千斤頂之推力及監測資料,以免造成意外災害之發生。

Pipe Jacking Method Applied to Underground Pedestrian Passage

The Xinzhuang line's Touqianzhuang Station is located beneath the Siyuan Road underground pedestrian passage at the intersection of Zhongzheng Road and Siyuan Road and near the traffic entrance of Dahan Bridge. The construction site is also near the transportation hub of Sanchong, Xinzhuang, and Banqiao districts, and is intertwined with myriads of underground utility pipelines which could not possibly be relocated no matter how much money is spent on them. In addition, due to a very limited construction site area, the station could not be constructed using the cut-and-cover method as suggested in the original design. Instead, construction was carried out at sidewalks, outer lanes of roads, and the spaces between Dahan Bridge piers by using an alternative pipe jacking method.

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