JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2015, Vol. 39 ›› Issue (06): 125-130.doi: 10.3969/j.issn.1000-2006.2015.06.022

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Vertical freezing reinforcement and monitoring in site for tunnel shield-launching end in soft soil stratum

SHI Quanbin1,2,YANG Ping1*,ZHANG Ting1,HE Dong1   

  1. 1.Civil Engineering Institute, Nanjing Forestry University, Nanjing 210037,China;
    2.Architectural Engineering Institute of Taizhou Polytechnical College,Taizhou 225300,China
  • Online:2015-11-30 Published:2015-11-30

Abstract: Shield launching and receiving are the key risk points in process of building subway tunnel, so the soft soil around the tunnel shield-launching end must be reinforced in order to ensure the shield launches safely. This paper took the left tunnel shield-launching end of Tianhe Road station Ning-he intercity rail in Nanjing City as background. The methods of soil reinforcement, the schemes of vertical partial freezing reinforcement to blocking water, the contents of monitoring, the layouts of temperature measuring tubes and measuring points, the layouts of probe holes, and the methods of inspection for tunnel shield-launching end were all put forward. The laws of temperature development were analyzed after the completion of monitoring in site, in addition, the necessary conditions which the monitoring in site should meet were put forward when shield began launching. The vertical freezing and the actual engineering practices proved that refrigerator shutdown would have a marked impact on freezing period, and recovery time was 2-3 times shutdown time. The methods of vertical partial freezing, and the layouts of double rows of freezing pipes were reasonable and effective. The monitoring schemes of laying temperature measuring tubes between the first row of freezing pipes and the diaphragm walls, between two rows of freezing pipes, outside of the outer rows of freezing pipes, and the methods of verifying freezing effect by experimental drilling were safe and reliable.

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