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Sciences in Cold and Arid Regions ›› 2022, Vol. 14 ›› Issue (4): 259–266.doi: 10.1016/j.rcar.2022.09.004.

• • 上一篇    

  

  • 收稿日期:2021-10-11 接受日期:2022-01-14 出版日期:2022-08-31 发布日期:2022-09-30

Frozen curtain characteristics during excavation of submerged shallow tunnel using Freeze-Sealing Pipe-Roof method

Ye Niu1,ZeQun Hong2(),Jun Zhang3,Lei Han4   

  1. 1.China Railway Siyuan Survey and Design Group Co. , Ltd. , Wuhan, Hubei 430056, China
    2.School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
    3.CCCC Second Highway Consultants Co. , Ltd. , Wuhan, Hubei 430056, China
    4.Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
  • Received:2021-10-11 Accepted:2022-01-14 Online:2022-08-31 Published:2022-09-30
  • Contact: ZeQun Hong E-mail:zqhong@cumt.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(52108386)

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Abstract:

The Freeze-Sealing Pipe-Roof (FSPR) method, which has been applied for the first time in the Gongbei Tunnel of the Hong Kong-Zhuhai-Macao Bridge, is a new approach of tunnel pre-support that allows flexible adjustment of freeze tube arrangement and can be adapted to different environmental conditions. When the FSPR method is used to construct shallow burial submerged tunnels, the frozen wall to hold back groundwater during excavation will be weakened by air and water flows inside and outside the tunnel, and its waterproof performance needs to be further investigated. In this paper, a two-dimensional numerical model of the temperature field considering excavation and moving water boundary is established based on the preliminary design scheme and in-situ conditions and is used to analyze the variation in frozen curtain properties with various active freezing times during excavation. The results show that excavation has a weakening effect on both sides of the frozen wall, with a greater effect on the inner side, and a positive temperature appears in the local area inside the jacked pipe. The concrete fill in the jacked pipe obviously improves the freezing efficiency, and the tunnel excavation after 60 days of active freezing in the interval filling mode can ensure that the frozen soil thickness at the thinnest segment exceeds 2 m, i.e., the design requirement. In practice, the active freezing time can be extended appropriately to reduce the influence of river water flow above the tunnel. The study serves as a technical reference for the design and implementation of similar projects.

Key words: Freeze-Sealing Pipe-Roof method, submerged tunnel, soil excavation, temperature field, frozen wall thickness

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LayerSoil

Thickness

(m)

Natural moistureDensity (g/cm3)

Natural

void ratio

Internal friction angleElastic modulus (MPa)
ρρd
(1)2Plain fill2.726.42%1.962.720.78--
(2)1Silty clay (soft, plastic)1.527.53%1.962.720.7811.64°16.2
(2)2Silty clay (hard, plastic)5.126.73%1.952.730.7711.18°18.0
(2)9Silty clay (hard, plastic)6.324.39%2.022.720.6816.00°24.5
(3)2Silty clay (hard, plastic)4.324.20%1.982.720.7212.50°21.8
(3)9Coarse gravel soil4.125.46%2.012.730.7013.00°25.0
(6)6-2Argillaceous sandstone2.623.33%2.012.740.7425.00°1.29×104
(6)5-3Sandstone-22.10%2.412.750.6654.70°1.57×104

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SoilParameter
Temperature (°C)Thermal Conductivity (W/(m·K))Density (kg/m3)Specific heat (J/(kg·K))Enthalpy (kJ/m3)
Frozen soil-281.741,8701,6500
-101.7455,714.4
-41.74115,302.2
Freezing point-2.11.74--199,526.7
Unfrozen soil181.42--247.954
Steel-44.707,850459.8-
Concrete-1.8352,344752.4-
Air-0.027911,003.2-

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