Study On Partition Protection Of Pile Adjacent To Metro Shield Tunnel Construction In Changsha Sandy Cobble Stratum

:Generally, partition protection of structure is used for a temporary protection measures, the design of which has a large experienced characteristic and the effect of which is uncertain largely. Therefore, research on partition protection of structure adjacent to metro shield tunnel construction has great significance. Based on the project of Changsha metro shield tunnel passing through L ramp of Xin-Zhong road interchange bridge in sandy cobble stratum, this article studies the features of ground surface settlement induced by metro shield tunnel and the partition protection of pile adjacent to metro shield tunnel through numerical analysis and field monitoring. The main studies and results in this paper are as follows:(1) Construction risk analysis is carried out in specific geological environment. As the construction risk of this project is very high, the control measure, jet grouting pile reinforcement, is proposed in order to avoid the related risks effectively and guarantee the safety of superstructure.(2) This article investigates the features of the sandy cobble stratum in Changsha metro. The characteristics of the ground surface settlement and optimized excavation parameters are also analyzed and summarized, which can provide a reference for similar projects. Meanwhile with the displacement controlled method this article predicts the ground surface settlement and compares with results got by the field monitoring.(3) By analyzing the influence of partition structure on stratum deformation, the action mechanism of partition structure is studied. And design parameters, like E1(stiffness of the partition structure), tanφ(vertical range of partition structure) and h(depths of partition structure), relevant to the partition structure are also analyzed. Actually they can be the basis for the optimization design of partition structure. In addition the partition structure can be used in homogeneous layers, the partition effect in soft and hard layers is also discussed. It turns out that partition protection measures are more suitable to soft and hard layers.(4) In order to analyze the effect of partition protection measures, by means of three dimensional numerical analysis (Ansys), this article investigates the responses of piles adjacent to shield tunnel while partition protection measures is or isn’t taken with the section having the highest risk during the excavation of the tunnel. The comparisons between the calculated and measured data validate the effect of the partition structure.