基于应力释放的大直径盾构隧道地表沉降分析

在城市环境及复杂地质条件下修建盾构隧道极易出现地面沉降塌陷,盾构隧道开挖引起的地表沉降分析与控制尤为重要。为了探究大直径盾构隧道地表沉降规律,以京张高铁清华园大直径盾构隧道为工程背景,基于应力释放及地层损失理论,首先运用有限差分软件建立二维模型,得到盾构掘进开挖的应力释放率;然后基于此建立三维数值模型,通过Peck公式反算得到清华园隧道盾构掘进引起的地层损失率,通过4种不同工况的模拟,对比分析不同掌子面释放系数、盾构机反力释放系数及脱空层模量缩放系数情况下的盾构隧道地表沉降规律,得到盾构施工现场导致的地层应力释放系数为0.12～0.14,相应的地层损失率为0.40%～0.47%;隧道轴线两侧20 m(1.6D)范围内为显著影响区,地表沉降主要发生在盾构通过这个阶段,约占总沉降量的50%。

Surface Settlement Analysis of Large-diameter Shield Tunnel Based on Stress Release Rate

Under the urban environment and complex geological conditions, the ground settlement is very likely to occur in the construction of shield tunnel. In order to explore the surface settlement law of large-diameter shield tunnel, this paper takes the large-diameter shield tunnel of Beijing-Zhangjiakou High-speed Railway Tsinghuayuan Tunnel as the engineering background, based on the theory of stress release and ground loss. Firstly, the finite difference software is used to build a two-dimensional model to obtain the stress release rate of shield tunneling. Then the ground loss rate caused by shield tunneling is calculated with Peck formula based on the three-dimensional numerical model. According to the simulation of four different conditions, the surface settlement of shield tunnel is analyzed in view of different tunnel face release coefficient, reaction of shield machine release coefficient and scaling coefficient of pavement layer modulus. The results show that the stress release coefficient caused by shield tunneling is about 0.12～0.14, and the corresponding ground loss rate is about 0.40%～0.47%. The significant influence area is within 20 m(1.6 D) on both sides of the tunnel axis, and the surface settlement mainly occurs in the shield passing stage, covering about 50% of the total settlement.