Abstract
With the advantages of fast construction speed and small disturbance to stratum, shield tunneling is becoming the preferred construction scheme for metro construction. However, if the disturbance of stratum cannot be clearly understood, it will affect the safety of adjacent underground structures and aboveground buildings. Based on the construction of the interval tunnel between Shizishan station and Chuanshi station of Chengdu metro line 7 project, this paper proposed a simplified calculation method to analyze the impact of shield excavation on adjacent pile foundation. A two-stage method of modified Peck formula and Winkler elastic foundation model was used to investigate the additional displacement and internal force of pile. A three-dimensional numerical model validated with the field test data was performed to compare with the theoretical results. The impact factors and their impact degree were discussed. The results show that the additional displacement and internal force are at a reasonable and acceptable level. The permanent pile foundation should adopt the small diameter pile as far as possible. When the small diameter pile foundation cannot meet the stress requirements, the design scheme of the pile group should be adopted. The area around shield tunnel is divided into strong impact area of pile foundation (S ≤ 0.75 D), slight impact area (0.75 D ≤ S ≤ 1.5 D), and no impact area (S > 1.5 D). The pile researched in this paper (S = 0.83 D) is in the slight impact area.
Highlights
With the continuous progress of urbanization in China, the urban population is growing, and urban traffic pressure is increasing
Shield tunneling has many advantages as mentioned above, and the construction technology has made great progress after many years of development, due to the defects of geological conditions and construction technology, the advance of shield tunneling will inevitably make a disturbance on the stratum, change the stress state of soil, and cause additional internal force and deformation of adjacent buildings and pipelines
Based on the two-stage method of modified Peck formula and Winkler elastic foundation model, this paper studied the impact of shield tunnel construction on adjacent pile foundation and analyzed the mechanical state of pile foundation and its impact factors by theoretical derivation and numerical simulation
Summary
With the continuous progress of urbanization in China, the urban population is growing, and urban traffic pressure is increasing. Shield tunneling has many advantages as mentioned above, and the construction technology has made great progress after many years of development, due to the defects of geological conditions and construction technology, the advance of shield tunneling will inevitably make a disturbance on the stratum, change the stress state of soil, and cause additional internal force and deformation of adjacent buildings and pipelines. If the disturbance of stratum cannot be clearly understood, it will affect the safety of adjacent underground structures and aboveground buildings Among these potential safety hazards, the problem of shield tunneling closely passing through bridges or building piles is one of the most frequently encountered. Based on the two-stage method of modified Peck formula and Winkler elastic foundation model, this paper studied the impact of shield tunnel construction on adjacent pile foundation and analyzed the mechanical state of pile foundation and its impact factors by theoretical derivation and numerical simulation. According to the variation degree of additional internal force of pile foundation, the stratum around the tunnel is divided into a strong impact zone, weak impact zone, and no impact zone, which can provide guidance and reference for the design and construction of similar underground projects in the future
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