Deformation Prediction of Existing Tunnel under Excavation Unloading Considering Rheological Effect

Abstract In the crossing engineering, the existing structure will produce corresponding stress and deformation due to the change of the stress state of the soil, while the soil in the soft soil area has rheological properties, and the deformation of the existing structure will be a time‐related process. In order to study the influence of excavation unloading of a new tunnel on the structural deformation of an existing tunnel in soft soil foundation, the finite element software is used to simulate the piercing project of a pipe jacking tunnel in Ningbo. The mapping relationship between soil rheological parameters and field monitoring displacement is established by BP neural network, and the inverted soil rheological parameters are obtained. the calculated deformation of the existing tunnel structure is basically consistent with the measured displacement. It is proved that the inversion results meet the requirements of engineering accuracy. The soil mechanical parameters obtained from the back analysis are forward analyzed in the finite element software to predict the long‐term deformation of the existing tunnel after the completion of the construction. The results show that the deformation development rate of the existing tunnel structure is faster in the first 30 days, then slows down gradually, and the uplift deformation of the existing tunnel structure tends to be stable on the 120th day.