富水粉细砂层大直径盾构隧道联络通道施工关键技术研究——以孟加拉卡纳普里河底隧道为例

Study on Key Construction Technology for Cross Passages in Large-diameter Shield Tunnels in Water-bearing Silty Fine Sand Stratum:A Case Study of the Karnaphuli River Tunnel Project in Bangladesh

  • 摘要: 孟加拉卡纳普里河底隧道工程2#联络通道位于河底中心全断面富水粉细砂地层,该通道施工具有开挖直径大、水土压力高的特点。为确保在海外应急抢险资源匮乏条件下江心联络通道安全施工,从冻结孔布置和钻设、隧道临时支撑结构、开挖构筑施工等方面提出综合技术措施:(1)冻结孔布置采用内外双圈、底部兜底设计;(2)冻结孔钻设采用分步开孔、低速慢进跟管、变径锥体接头快速封堵的工艺;(3)洞口加强型环形框梁结构代替主隧道环梁钢支撑结构;(4)采用分区作业、快速导洞施作、台阶法开挖、反临空扩挖、随挖随支的施工工艺;(5)采取快速冻结、自然解冻、跟踪注浆降低冻胀融沉影响。最后对重大风险点进行分析预判并制定相应的预防措施,冻结孔温度及主隧道衬砌结构变形监测数据证明,该技术可确保大直径盾构隧道联络通道的顺利完成,成功的施工经验可为国内外类似项目提供借鉴和经验。

     

    Abstract: The No. 2 cross passage of the Karnaphuli River Tunnel Project in Bangladesh is located in a water-bear? ing silty fine sand stratum below the river bottom center. This cross passage is characterized by large excavation diameter and high water and soil pressure. In order to ensure safe construction of the cross passage in the middle of the river when there is shortage of overseas emergency rescue resources, comprehensive technical measures have been proposed from aspects such as freezing hole layout and drilling, temporary support structure of tunnel, excavation and structure construction: (1) The freezing holes are arranged in inner and outer circles, with supporting features at the bottom; (2) Freezing hole drilling process is conducted by means of step-by-step boring, slow pipe advancing and fast plugging by reducing tapered joint; (3) The steel support structure of ring beam in the main tunnel is superseded by the reinforced annular frame beam at the tunnel portal; (4) The construction process is conducted by means of zoned works, fast pilot tunnel construction, excavation by bench-cut method, expanded excavation opposite to free face and excavation-and-support method; (5) The effects of frost heave and thaw settlement are reduced by fast freezing, natural thawing and track grouting. At last, the major risk points are predicted and analyzed,and the preventive measures are prepared accordingly. As proven by the data from freezing hole temperature monitoring and main tunnel lining structure deformation monitoring, this technology will ensure successful construction of cross passage of large-diameter shield tunnel. Such successful construction experience can be valuable reference in other similar projects at home and abroad.

     

/

返回文章
返回