In order to ensure the safety of the construction of the subway double-line shield tunneling of long distance and parallel running under the existing buildings, the FLAC3 Dfinite difference software is used to build the model to obtain the deformation rule and influence range t of the building structures caused by the construction of subway shield tunnel.Results show that: (1) according to the theoretical calculation and practical monitoring, the influence of shield tunnel construction on existing buildings focuses on 20 m horizontally above and along the two sides of the tunnel, thus, the building structures in this range should be monitored closely; (2) to reduce formation damage caused by shield construction, it is necessary to conduct the secondary lining in a timely manner to the lateral strata where the segments of the tunnel arch are located under the existing buildings, and the monitoring shows that the largest absolute structure settlement is about 9.5 mm and the largest difference settlement is 10.5 mm, which all meet the safety indexes required by assessment authority; (3) using automated monitoring, keeping track of the building deformation data and adjusting such tunneling parameters as shield thrust, soil storehouse pressure and advance rate can minimize the disturbance to the existing buildings.%为确保地铁双线盾构隧道长距离平行下穿既有建筑物的安全,采用FLAC3D有限差分软件建立模型,获得施工过程中地铁盾构隧道所引起的该建筑结构的变形规律及影响范围,并提出针对性的监测方案.结果表明:(1)根据理论计算及实际监测,盾构隧道施工对既有建筑结构的影响范围为隧道上方及两侧20 m横向范围,因此应对该范围内的建筑结构进行重点监测;(2)为降低由于盾构施工造成的地层损失,及时对区间下穿既有建筑段下方隧道拱部管片外侧地层进行二次注浆加固很有必要,通过监测可知,该建筑结构最大绝对沉降值约为9.5 mm,最大差异性沉降值为10.5 mm,均满足评估单位给出的安全指标;(3)采用自动化监测手段,实时掌握建筑物的变形数据,通过调整盾构推力、土仓压力、掘进速度等掘进施工参数,最大程度降低对既有建筑结构的扰动.
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