When predicting ground surface settlement caused by constructing a new tunnel beneath existing structures, traditional stochastic medium theory inadequately accounts for the effects of abrupt changes in the cross-sectional areas of variable-section tunnels and the presence of existing structures, potentially leading to significant errors. In this paper, an enhanced ground surface settlement prediction model, based on stochastic medium theory, is proposed. The model equates the settlement of the existing structure’s base slab to that of the overlying soil and divides the horseshoe-shaped tunnel cross-section into eight arc segments, which are calculated using a polar coordinate system. Furthermore, the model treats soil loss at the junctions of variable-section tunnels as a linear transition, introduces the concept of a linear transition segment for variable sections, and accounts for the superimposed effects of closely spaced twin-tunnel excavations. Based on this model, a general-purpose calculation program has been developed that enables the rapid prediction of ground surface deformation caused by a variable-section tunnel passing beneath existing structures, simply by inputting engineering parameters. Finally, the accuracy of the prediction model was validated through comparisons with field measurement data, finite element analysis results, and calculations based on traditional stochastic medium theory. The results indicate that the proposed prediction model demonstrates high consistency with field data and finite element analysis results, whereas traditional stochastic medium theory results exhibit significant errors. This model is scientifically valid and provides a reliable reference for predicting ground surface settlement in comparable variable-section metro tunnel construction projects.

中文翻译：

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基于随机介质理论的既有结构下变截面隧道施工时地表沉降预测模型


在预测在现有结构下建造新隧道引起的地表沉降时，传统的随机介质理论没有充分解释变截面隧道横截面积突变和现有结构存在的影响，这可能导致重大误差。该文提出了一种基于随机介质理论的增强型地表沉降预测模型。该模型将现有结构底板的沉降等同于上覆土壤的沉降，并将马蹄形隧道横截面划分为八个弧段，这些弧段使用极坐标系计算。此外，该模型将变截面隧道交界处的土壤流失视为线性过渡，引入了可变截面的线性过渡段的概念，并考虑了紧密间隔的双隧道开挖的叠加效应。基于该模型，开发了一种通用计算程序，只需输入工程参数，即可快速预测变截面隧道通过现有结构下方引起的地表变形。最后，通过与现场测量数据、有限元分析结果的比对和基于传统随机介质理论的计算，验证了预测模型的准确性。结果表明，所提出的预测模型与现场数据和有限元分析结果具有高度一致性，而传统的随机介质理论结果存在显著误差。 该模型具有科学有效性，为预测同类变断面地铁隧道建设项目的地表沉降提供了可靠的参考。