以北京地铁9号线某区间隧道近接既有铁路桥梁施工为背景,文章基于Hardening-soil本构模型采用三维数值计算与现场实测结果相对比的方式,研究卵石地层地铁隧道近接既有铁路桥施工的位移特征.研究得出的结论为:(1)卵石地层岩体较为松散,胶结性较差,围岩稳定性较低,可引入Hardening-soil模型模拟其应力-应变关系;(2)区间隧道开挖引发的竖向位移主要集中在隧道拱顶部位,并随着向地层深部的发展逐渐衰减;(3)地铁区间隧道施工引发的地表沉降可认为是两条单洞隧道地表沉降曲线的叠加,现场实测与数值计算得出的规律一致;(4)既有铁路桥结构最大位移值小于《铁路线路修理规则》的容许位移,现有开挖方式和支护参数满足既有结构安全运营条件;(5)地铁区间隧道开挖引发的地层、既有桥梁结构水平位移整体较小;(6)区间隧道开挖引起的土体扰动主要集中在隧道洞周5.4 m范围内.%Taking a running tunnel approaching an existing railway bridge as an example, the characteristics of dis?placements induced by metro tunnel construction approaching an existing railway bridge are studied using the Hard?ening-Soil constitutive model, which compares 3D numerical calculations and site measured results. The following conclusions are made: 1) the rock of a cobble stratum is relatively loose and has poor cementation and stability of the rock mass, and the Hardening-Soil model may be used to simulate the stress-strain relation;2) vertical displace?ment induced by running tunnel excavation is mainly concentrated at the tunnel crown and decreases gradually with the increasing of the overburden;3) surface subsidence induced by the tunnel excavation may be regarded as the su?perposition of the surface settlement curves of two single-bore tunnels, and the measured values are consistant with the calculated values;4) the maximum deformations of the existing railway bridge are smaller than the allowable dis?placements specified in"Railway Line Repair Rules,"and the existing excavation method and support parameters meet the operating conditions for the existing structure regarding its safety;5) generally the excavation-induced hori?zontal displacement of the stratum and existing bridge structure is small;and 6) the running tunnel excavation-in?duced soil disturbance is mainly within the range of 5.4 m around the tunnel.
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