遮拦叠交效应下地铁盾构掘进引起地层沉降分析

 地铁隧道施工诱发的土体沉降以及临近地下构筑物变形是我国城市轨道交通施工安全控制和风险评估中较为关心的一类施工问题。目前，针对该领域地层沉降的简化理论研究还仅仅针对自由位移场，没有考虑临近既有构筑物的遮拦效应影响。依托上海在建地铁施工工程实践，采用简化理论方法、三维有限元数值模拟方法以及现场监测方法，分析考虑运营隧道遮拦效应影响的土压平衡盾构施工引起的周围土体沉降规律，并与自由位移场条件下盾构施工引起的地层变形进行对比分析；在此基础上，给出地铁盾构复杂叠交穿越引起的临近地铁隧道的变形规律。研究表明，本文提出的简化理论方法和三维有限元数值模拟方法可以较好地模拟遮拦叠交效应下地铁盾构掘进引起的地层沉降变形；临近既有建(构)筑物施工，盾构施工引起的周围土体沉降较大程度地受到遮拦效应影响，与自由位移场条件下的计算结果对比存在较大差别。最后，结合盾构施工监测数据，提出复杂遮拦叠交效应下的盾构叠交施工变形控制技术措施。成果可为合理制定施工场地存在复杂建(构)筑物工况条件的地铁隧道开挖对周围环境保护措施提供一定的理论依据。

ANALYSIS OF GROUND SETTLEMENTS INDUCED BY SUBWAY SHIELD EXCAVATION CONSIDERING SHELTERING OVERLAPPED EFFECTS

Ground settlements and underground structure deformation induced by subway tunneling are hot issues in the underground transportation construction safety control and risk assessments. Previous researches on ground settlements are basically concentrated on the soil free displacements，and the sheltering effects of adjacent existing underground structures are not considered. Based on the Shanghai tunneling case，the ground settlement rules induced by earth pressure balance(EPB) shield considering sheltering effects of tunnels in service are presented by using simplified analytical method，3D finite element(FE) numerical simulation method，and in-situ monitoring method. An in-depth analysis is conducted between ground settlements considering sheltering effects and those considering free soil displacements. In addition，the predicted deformation of subway tunnel induced by EPB shield during complex overlapped traversing process is also presented. It is observed that the simplified analytical method and 3D finite element method can perfectly simulate the ground movements induced by subway shield excavation considering sheltering overlapped effects. Furthermore，the sheltering effects have a major influence on ground settlements induced by EPB shield when the tunnels are excavated in the vicinity of existing buildings and structures. The differences compared with the results considering free soil displacements are obtained. Finally，the deformation controlling technical measures considering sheltering overlapped effects are proposed in combination of in-situ monitoring data. It may provide certain basis to build up correctly protective measures of geotechnical environments influenced by subway tunneling，especially the sites adjacent to existing buildings and structures.