摘要:
福州市地铁一号线需穿越江心小岛,并在岛上设置盾构换刀区,换刀区域开挖面需稳定性加固。开挖面上部为中细砂层,透水性强,稳定性差。设计采用MJS工法,加固兼止水,成桩直径≥2200 mm,搭接700 mm。岛上5.6 m以浅为杂填土层,向下依次为淤泥、中砂、细砂层, MJS钻杆成孔难度大,抱钻杆及埋钻杆的风险极大。大功率顶驱钻机采用双管钻进轻松穿过回填层和砂层,在砂层中留置一定深度的外套管兼作护套管,可以起到一定的防塌孔功能,成功解决了复杂地层用MJS工法施工的引孔难题。
Abstract:
Fuzhou subway Line 1 was planned to cross an island in middle of the river and the shield tool changing area was to set up on the island.Stability reinforcement should be made for excavation face of tool changing area;the upper part was medium-fine sand with strong permeability and poor stability.MJS method was adopted in the design for strengthening and water sealing with pile diameter≥2200mm and overlapping 700mm.On the island, there was 5.6m thickness of miscella-neous fill layer, followed by silt, medium sand and fine sand layers, drilling was difficult for MJS method because of the risks of drill pipe holding and burying.High-power top drive drilling rig can easily pass through backfill and sand layers with double-pipe.A certain length outer casing was retained in the sand as protecting casing to prevent hole collapse, guide-hole difficulties for MJS construction method in complex strata were successfully resolved.
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