Large-scale pits excavation above underground structures can lead to the uplift of these structures.Accurate prediction of the uplift deformation is a prerequisite for reasonably assessing the impact of pit excavation.This paper takes the large-scale pits excavation above existing shield tunnels of the subway as the background.Based on the distribution law of additional loads during pit excavation and the layered summation method,the response displacement of the shield tunnel under the conditions of pits excavation and internal stacking is divided into four parts:overall uplift displacement,relative uplift displacement,compression displacement due to stacking,and special geological additional displacement.The theoretical calculation method for tunnel uplift displacement is proposed separately for each part.To verify this calculation method,it is applied to estimate the tunnel uplift displacement in a project in Nanning.A comparison between the calculation and the monitor data shows that the overall uplift of the layers caused by large-scale excavation accounts for the largest proportion of the tunnel uplift,while the internal stacking measures have a significant effect on limiting the tunnel uplift during shallow excavation.The theoretical calculation method is more suitable for predicting the uplift displacement of the shield tunnel in the stable stage after the completion of construction.The calculated results are in good agreement with the measured data of the project,with an error of no more than 10%.This can provide a reference for the design and construction of similar projects.
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