大型深基坑开挖对旁边地铁盾构隧道影响的实测分析
Monitoring data analysis on the influence of large deep foundation pit excavation on nearby metro shield tunnel

杭州地铁2号线旁边某深基坑开挖工程，采用“坑中坑”和“地下连续墙外再增设一排同深度的隔离桩并用连梁连接”的特殊加固控制措施。对基坑开挖引起临近隧道的水平位移、竖向位移和水平收敛进行监测，分析大型深基坑开挖对旁边地铁隧道的影响规律以及支护加固措施的效果，并提出隧道水平位移的预测经验公式。研究结果表明：基坑开挖导致隧道产生明显的正态分布水平向变形，隧道横向直径增大，呈现“横椭圆”形状，但变形符合规范要求；隧道沉降未超过工程报警值。本工程采用的加固控制措施适用于大型深基坑工程，建议土体必须采取“分块开挖、随挖随撑、分层浇筑”的方式，减小靠近隧道侧的基坑开挖暴露宽度。
The large deep foundation pit adjacent to the Hangzhou Metro Line 2, pit-in-pit excavation and the binding beam connecting underground diaphragm wall and a row of the same depth of isolation pile are used as special reinforcement measures. Horizontal displacement, vertical displacement and horizontal convergence of the tunnel caused by excavation are monitored. Rules of the influence of large deep excavation on the nearby tunnel and effect of reinforcement measures are analyzed. Empirical formulas of horizontal displacement of the tunnel is proposed. The results show that the horizontal deformation of normal distribution in tunnel increases obviously and transverse diameter of tunnel increases obviously that leads to the tunnel shows a shape of the horizontal ellipse. The horizontal displacement and convergence of the tunnel satisfies the codes and settlement satisfies the alarm value which is settled. The reinforcement measures of the project are applied to large deep foundation pit. “Step excavation, cut-and-support, step concrete placing” should be taken as excavation methods and width which is exposed of foundation pie adjacent to tunnel caused by excavation can be decreased