隧道近接下穿既有铁路线低扰动施工方法及其精细化模拟分析

Construction Method with Low Disturbances and Detailed Simulation Analysis of Tunneling Through Railway Bridges

针对软弱地层中某新建隧道近距离侧穿2条相邻铁路线大桥桩基础的特殊工程需求,提出并设计了一套新式强化联合支护方法;针对性地建立了三维精细化数值模型,并设计了基于无限元法的边界处置技术,有效地控制了边界效应与模型规模;实现了在新式强化联合支护方法下,对新建隧道开挖的全过程进行工程尺度模拟;量化分析了新建隧道施工过程对既有桥墩结构、超近接桩基水平位移、竖向沉降和应力分布的影响。结果表明:在拟定设计支护结构参数和施工方法的条件下,新建隧道下穿既有铁路大桥桥墩的施工,对桩基的位移变化影响相对较小,各指标最大变形均未超过相关规范允许的控制值;各桥梁桩基受施工影响而导致的应力幅值变化较小,普遍处于受压状态,压应力小于桩体材料的最大应力容许值。该研究结果对相似工程的施工和安全稳定控制有借鉴意义。

A novel union support strategy is proposed to ensure the safety of a new tunnel through two close railway bridges in a weak stratum;Next,a 3D detailed numerical model is established.The boundary treatment technology based on infinite elements are designed to control the boundary effects and the model size;The overall excavation process is scale simulated by new strengthening combined support;The influences of tunneling on the existing bridge piers,horizontal displacement of the ultra-near pile foundations,vertical settlement and stress distributions are quantitatively analyzed.The results show that the newly built tunnel through the existing railway bridge piers will less impact the displacement of the pile foundation under the designed supporting structure parameters and construction methods.The maximum deformation of each index is no more than the admissible control value of the relevant specifications;The changes in pile stress are also limited and acceptable.The pile the stress of each pile foundation cause by the construction change small and is generally under compression.The compressive stress is less than the the maximum stress of the pile materials.This research can provide references for similar engineering construction and safety control.