摘 要 擁擠的都市地下空間中，進行軟弱土層大斷面的隧道開挖及近接隧道施工的案例日益增多。潛盾隧道施工過程中，由於地盤應力的變化，造成鄰近周邊地盤的變形，也造成既存隧道鄰近及結構物產生下陷、傾斜甚至結構體破壞。鄰近既存隧道旁挖新隧道時，可能造成營運中的既存隧道受損，因此如何對既存隧道的保護或新挖隧道的施工掘進管理成為相當重要的工作。 潛盾隧道施工常遭遇的問題包含：(1)隧道開挖面之穩定性檢討；(2)施工引致地表沈陷分佈與對建物之影響評估；(3)作用於環片之土壓力大小評估。 針對潛盾施工問題，故本研究之重點分為三大主題：第一部份探討單隧道開挖穩定問題，由於開挖的過程中，鄰近地表面之隧道開挖面穩定分析是一個複雜的三向度問題，故以離心模型試驗探討單隧道開挖面破壞所引致之地表沈陷分佈狀態、隧道周圍孔隙水壓之變化及隧道破壞後之地盤變化與破壞型態；第二部份探討單隧道盾尾間隙閉合後地盤應力釋放作用在環片上土壓力大小，用以決定隧道環片之強度及架設時機；第三部分探討新建隧道掘進推力、盾尾間隙閉合及背填灌漿壓力等施工過程，對既存隧道局部土壓力變化之關係。上述模型試驗成果，將與現場糧側結果進行比對，檢核其正確性。 ABSTRACT In order to reduce the environmental impacts in crowded cities the neighboring shield tunneling construction works have obviously increased recently. The change of ground stresses due to tunneling processes would cause the displacement of ground nearby a tunnel. Structures sit on it may settle, tilt and even fail. It is a key issue to provide an appropriate measure to avoid a pre-exist tunnel system being exposed to danger as a result of new neighboring shield driven. The problems a designer often faces on construction of the shield tunnel in soft ground are：(1) the face stability of a tunnel; (2)influence of the magnitude and extent of surface settlement trough caused by tunneling on the safety of building nearby a tunnel; (3)estimate of the earth pressure on tunnel segments. This study emphasize in three key subject：(1)During excavation, the face stability analysis of a shallow tunnel is a complex three-dimensional problem. Therefore, a series of single tunnel centrifuge model embedded in soft soils was used to investigate the distribution of surface settlement troughs, the changes of pore water pressure and the collapse mechanisms around the tunnel; (2)A series of three-dimensional models with cover-to-diameter ratios 2 are used to investigate the earth pressure acting on liner after tail voids closure and on the liner of a existed tunnel due to nearby new tunneling; (3)This aims at to investigate the earth pressure change caused by face supporting pressures, back grouting pressure and tail voids convergence during tunnel construction process using a centrifuge tunnel model. The test results will be compared with the field data to check the validity of the proposed method.