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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
(1. CCCC SHEC Third Engineering Co., Ltd., Zhenjiang 212021; 2. CCCC Second Harbor Engineering Company Ltd., Wuhan 430040;3. R&D Center for Intelligent Manufacturing Technology of Transportation Infrastructure in Transportation Industry, Wuhan 430040;4. Key Laboratory for Long and Large Bridge Construction Technology in Transportation Industry, Wuhan 430040)
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and fast plugging by reducing tapered joint; (3) The steel support structure of ring beam in the main tunnel is superseded by the reinforced annular frame beam at the tunnel portal; (4) The construction process is conducted by means of zoned works, fast pilot tunnel construction,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.
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.
HAN Xiaoming1,
2 HE Yuan1,
2 ZHANG Feilei2 etc
.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[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(3): 227-235
2023, Vol. 60 