地铁区间极小间距下穿高铁盾构隧道施工方法分析

Construction Method Analysis for Metro Tunnel with Minimal Spacing under High-speed Rail Shield Tunnel

以北京12号线地铁区间极小间距下穿京张高铁盾构隧道为工程背景,数值模拟了台阶法、临时仰拱台阶法、CD法以及CRD法施工过程,揭示了下穿工程地层变形、地表沉降、盾构管片变形以及支护结构受力特征等规律。研究结果表明:地铁区间施工拱顶和仰拱围岩变形最大。地表最大沉降位于地铁双区间隧道中心截面,越靠近中心地层变形叠加效应越明显,距离超过20 m的地层主要受单线隧道施工影响,且变形大幅降低;地铁施工引起盾构管片最大变形在双区间中心截面±15 m范围内,为减小盾构隧道变形,可局部加固距地铁区间较近30 m段管片;在台阶法基础上设置临时仰拱后,不仅减小了初支因弯矩产生的应力,还能充分利用锚管的锁脚作用,临时仰拱台阶法有效控制了地层变形。

Based on the project of Beijing subway Line 12 passing through Beijing-Zhangjiakou High Speed Rail shield tunnel with minimal interval,this paper uses numerical solution to simulate the construction process of bench cut method,temporary inverted arch bench cut method,CD method and CRD method.It discusses some key issues such as the law of formation deformation in underground engineering,surface subsidence law and deformation law of shield tube sheet and stress characteristics of support structures.The results show that the deformation of arch top and invert surrounding rock is the largest in subway interval.The maximum settlement of the surface is located at the central section of the subway two-interval tunnel.The closer to the central stratum,the more obvious the superposition effect is.The stratum with a distance of more than 20 m is mainly affected by single-line tunnel construction,and the defomation is greatly reduced.The maximum deformation of shield tube sheet caused by subway construction is within the range of±15 m of the central section of the double interval.In order to reduce the deformation of shield tunnel,the local reinforcement can be done to 30m pieces of tube from the subway interval.After the temporary invert is set up on the basis of bench cut method,it not only reduces the stress caused by the bending moment of the initial branch,but also makes full use of the anchor pipe's locking foot.So the temporary inverted arch bench cut method effectively controls stratum deformation.