Abstract: The second phase of interval tunnel of the Chengdu metro line 4 is a two-line shield tunnel. It crosses a railway group, which includes ballastless track, ballast track and pile foundation railway bridge. Using a numerical simulation method, a 3D finite difference model of shield tunnel crossing railway bridge was built. Surface subsidence, soil deformation, and pier displacement caused by tunnel construction were analyzed in detail. The safety of the railway bridge was evaluated, and control measures were put forward. Based on soil reinforcement measures, two cases of a reinforced and non-reinforced soil mass were compared. The results show that the maximum horizontal displacement and vertical subsidence can be reduced by 58% and 79% after soil reinforcement, and that the values of settlement meet the safety requirements if the soil mass is reinforced.

Key words: tunnel engineering, shield tunnel construction, railway bridge, ground surface settlement, soil reinforcement, numerical model

摘要： 成都地铁4号线二期工程万年场站~东三环站区间为双线盾构隧道，区间盾构隧道下穿包括无砟轨道、有砟轨道及桩基础形式铁路桥的铁路 群。以数值模拟为手段，采用 Flac3D软件，建立盾构下穿铁路桥的三维有限差分模型，对盾构掘进中造成的地表沉降、周围土体变形及铁路桥墩 的沉降变化进行了分析，评价了上部铁路桥的安全性，并提出了相应的安全控制措施。基于土体加固措施，对加固与不加固工况进行了对比分析 。结果表明：铁路桥与盾构隧道间土体加固后，桩基最大水平位移和竖向沉降分别减少了58%和79%，桥墩沉降满足安全控制标准，盾构施工对铁 路桥运营的影响在安全范围内。

关键词: 隧道工程, 盾构隧道施工, 铁路桥, 地表沉降, 土体加固, 数值模拟