潛盾隧道通過社區下方之建物保護

介紹在粘土層中進行曲線雙隧道穿越建物下方之中和線案例。為避免施工引致地表變形過大損及鄰產,原規劃於潛盾隧道周缘以高壓噴射灌漿工法施作一地盤改良環,以截斷沈陷槽向外傳播,達到抑減沈陷之目的。惟因隧道係在建物下方,灌漿工作僅能採斜灌方式施工,經以單管、雙重管及三重管工法進行現場試灌,試灌結果顯示取樣率最低,實際成環效果並不理想;正式施工時初採HDD水平式灌漿,惟在施作第2個孔灌漿樁時發生施工點上方民房地坪隆起,故中止改良工作;在審慎評估潛盾施工程序與施工控制技術後,決定採嚴謹之潛盾施工品質配合背填灌漿後之二次注入灌漿工法,加上密集之監測管控方式施工,確實可以克服軟弱地層條件並有效將隧道施工引致之沈陷降至最低,達到建物保護目的。

BUILDING PROTECTIONS WITH SHIELD TUNNEL PASSING UNDER

The case that a shield tunnel passes under buildings in clay layers is introduced. To avoid potential damages to the existing buildings induced by the settlement, the original planning was to apply JSG method to cut off the outward propagation of the settlement by forming a ring around the shield tunnel. The site trials of the single-, double- and triple-tube grouting had failed because of the low sampling ratio. Then HDD method in construction period was also called a halt because ground heaving has occurred. The secondary compensation grouting following backfill grouting was employed after full evaluation on construction procedure and construction-control technique, and intensive monitoring was carried during construction. This method was proved to be effective in settlement mitigation for building protection.