大直径盾构隧道下穿高铁无砟轨道路基预加固方案研究

Study on Pre-reinforcement Scheme of Large Diameter Shield Tunnel Passing under Ballastless Track Subgrade of High Speed Railway

以某高速铁路大直径盾构隧道下穿既有沪宁高速铁路无砟轨道路基为背景,采用三维数值模拟方法并参考类似工程案例,研究3种不同防护方案下(管幕加固、竖井底部注浆、保压循环注浆方案)大直径盾构下穿既有高铁路基及轨道的变形控制效果和措施。研究结果表明:轨道高低应作为盾构下穿施工的主要控制指标,无防护措施下大直径盾构下穿软土地层造成的最大沉降值为28.56 mm,不利于轨道的平顺性控制,仅采用盾构掘进措施无法满足高铁安全运营;保压循环注浆方案下路基中心沉降3.13 mm,通过主动控制路基变形调节轨道变形,轨道高低值0.21 mm,轨向值0.23 mm,远小于作业验收控制值;基于既有高铁路基沉降控制要求,确定了保压循环注浆的合理注浆压力不宜超过40 kPa、注浆管间距不宜大于0.4 m等参数,为工程施工提供指导。

A planned high-speed railway shield tunnel crossing the ballastless track subgrade of the existing Shanghai-Nanjing High-speed Railway is taken as the engineering background, and the deformation control measures and effect of shield tunneling of large diameter under existing high-speed railway subgrade and track are studied with respect to the three different protection schemes of pipe roof method, grouting at the bottom of shaft, and pressure cycle grouting. The research results show that with the track height difference taken as the main control index of the shield tunneling underpassing construction, the maximum settlement value of large diameter shield passing through soft soil layer without protective measures is 28.56 mm, which is not conducive to the control of track smoothness, and shield tunneling measures alone to control the deformation can’t meet the safety operation of high-speed railway;the settlement of subgrade is only 3.13 mm with pressure cycle grouting scheme, and adjusting the track deformation by actively controlling the subgrade deformation can only achieve 0.21 mm track height and 0.23 mm track direction, which are far less than the acceptable operation control values;based on the settlement control requirements of the existing high-speed railway subgrade, the reasonable grouting pressure should not be greater than 40 kPa, and the grouting pipe spacing should not be greater than 0.4 m, which may provide guidance for engineering construction.