隧道开挖地表沉降动态预测及影响因素分析

城市地铁隧道施工不可避免地对围岩产生扰动引起地表沉降，动态预测隧道开挖引起的地表沉降是确保地表建构筑物与隧道施工安全的重要基础。针对隧道施工过程中地表沉降难以准确动态预测的问题，在定义纵向开挖度系数? 的基础上，建立横向地表沉降动态预测模型。该模型能够描述同一监测位置沉降曲线随掌子面推进而不断变化的规律，实现施工现场沉降动态预测。结果表明：在特定约束条件下，该模型能够退化为Peck模型以及随机介质理论预测模型；通过现场施工验证了该动态预测模型的准确性与适用性；基于纵向开挖度系数? 将隧道沿纵向分为强烈、中度和轻度共3个影响段，较好地反映了开挖掌子面在不同位置对同一监测截面的影响程度；通过分析建筑物和隔离桩对地表沉降曲线的影响可知，建筑物与其附近地层呈现出协同变形、共同承载的特征，在隧道一侧添加地质钻隔离桩对该侧地表沉降值的减小程度可达71.9%。研究成果对滇中引水工程现场施工与类似工程具有一定指导和借鉴意义。

Dynamic prediction and influence factors analysis of ground surface settlement during tunnel excavation

The construction of urban subway tunnel inevitably produces disturbance to surrounding rock and causes ground surface settlement. Dynamic prediction of ground surface settlement caused by tunnel excavation is an important method to ensure the safety of above-ground buildings and tunnel construction. In view of the difficulty of accurate dynamic prediction of ground surface settlement during tunnel construction, based on the definition of longitudinal excavation coefficient ? , a dynamic prediction model of lateral ground surface settlement is established. The model can accurately describe the variation of the settlement of the same monitoring location with the advancement of the tunnel face, and then realize the dynamic prediction of the ground surface settlement at the construction site. The results show that under certain constraints, this model can be degenerated into Peck model and stochastic medium theory prediction model. The accuracy and applicability of the dynamic prediction model are verified by on-site construction. The tunnel can be divided into three affected segments longitudinally (i.e., intense influence, moderate influence, and mild influence) based on the obtained ? , which well reflected the influence degree of the excavated tunnel face on the same monitoring section at different positions. Through the analysis of the influence of the buildings and isolation piles on the ground surface settlement curve, it can be found that the building and its adjacent ground surface present the characteristics of cooperative deformation and joint bearing. Moreover, installing geological drill isolation piles on the side of the tunnel can reduce the ground surface settlement of that side up to 71.9%. The research results have a certain guiding and reference significance for the on-site construction of the Central Yunnan Water Diversion Project and similar projects.