The Environmental Effects Induced by a Metro Shield Tunnel Side‐Crossing on Adjacent Pile Foundations and Its Impact Partition

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.

Three-dimensional Finite-element Analysis of the Influence of Tunneling on Pile Foundations

“…The effect of tunneling on pile foundations has been studied by many researchers using field data, experimental work, numerical modeling and analytical analysis (Jacobsz et al, 2002;Jacobsz et al, 2004;Lee et al, 2005;Kitiyodom et al, 2005;Pang et al, 2006;Selemetas et al,2006;Cheng et al, 2007;Shong-Loong Chen et al, 2016;Hui Hu et al, 2021).…”

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

“…Numerous scholars have studied the pile foundation settlement caused by shield tunnelling through analytical analysis, laboratory tests and numerical simulations. Hu et al (2021) proposed a simplified calculation method to analyse the impact of shield excavation on adjacent pile foundations. 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; Basile (2014) proposed an efficient analysis method is presented for estimating the effects induced by tunnelling on existing pile foundations; Lee and Jacobsz (2006) studied the effects of tunnelling on an existing pile constructed in weathered Abbreviations: q 1 , additional thrust inside the cutter head (kPa); q 2 , additional thrust outside cutter head (kPa); f 1 , inner shield friction resistance (kPa); f 2 , outer shield friction (kPa); p, additional grouting pressure (kPa); R, cutter radius (m); K, foundation reaction modulus (MPa); G c , stiffness of the shear layer (MPa); EI, bending stiffness of the pile; E s , elastic modulus of soil (MPa); R 0 , turning radius (m); L, shield length (m); µ, Poisson's ratio; g, formation loss parameter (m); H, depth of the cutter head (m); G, shear modulus of the soil (MPa); IGST, integrative gap at the shield tail; OG, over-cutting gap; D, diameter of the pile (m), t, the thickness of the shear layer (m).…”