Geomechanics and Engineering

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Field test and research on shield cutting pile penetrating cement soil single pile composite foundation

  • Ma, Shi-ju (School of Civil Engineering, Zhengzhou University) ;
  • Li, Ming-yu (School of Civil Engineering, Zhengzhou University) ;
  • Guo, Yuan-cheng (School of Civil Engineering, Zhengzhou University) ;
  • Safaei, Babak (Department of Mechanical Engineering, Eastern Mediterranean University)
  • Received : 2020.05.09
  • Accepted : 2020.12.10
  • Published : 2020.12.25
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Abstract

In this paper, due to the need for cutting cement-soil group pile composite foundation under the 7-story masonry structure of Zhenghe District and the shield tunnel of Zhengzhou Metro Line 5, a field test was conducted to directly cut cement-soil single pile composite foundation with diameter Ф=500 mm. Research results showed that the load transfer mechanism of composite foundation was not changed before and after shield tunnel cut the pile, and pile body and the soil between piles was still responsible for overburden load. The construction disturbance of shield cutting pile is a complicated mechanical process. The load carried by the original pile body was affected by the disturbance effect of pile cutting construction. Also, the fraction of the load carried by the original pile body was transferred to the soil between the piles and therefore, the bearing capacity of composite foundation was not decreased. Only the fractions of the load carried by pile and the soil between piles were distributed. On-site monitoring results showed that the settlement of pressure-bearing plates produced during shield cutting stage accounted for about 7% of total settlement. After the completion of pile cutting, the settlements of bearing plates generated by shield machine during residual pile composite foundation stage and shield machine tail were far away from residual pile composite foundation stage which accounted for about 15% and 74% of total settlement, respectively. In order to reduce the impact of shield cutting pile construction on the settlement of upper composite foundation, it was recommended to take measures such as optimization of shield construction parameters, radial grouting reinforcement and "clay shock" grouting within the disturbance range of shield cutting pile construction. Before pile cutting, the pile-soil stress ratio n of composite foundation was 2.437. After the shield cut pile is completed, the soil around the lining structure is gradually consolidated and reshaped, and residual pile composite foundation reaches a new state of force balance. This was because the condensation of grouting layer could increase the resistance of remaining pile end and friction resistance of the side of the pile.

Keywords

Acknowledgement

The research described in this paper was financially supported by the National Science Foundation of China (51508520), and remarkable assistance from China Railway 18th Engineering Bureau Group First Engineering Co. LTD.

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