Numerical Method for the Deformation Calculation of the Shallow Buried Tunnel Caused by the Excavation of Overlying Soil Based on Soil Rebounding Characteristics

In view of strict deformation control standards, it is important to calculate the shallow tunnel deformation caused by the unloading of overburdened soil for analyzing tunnel structure safety. Due to the obvious nonlinear characteristics and the significantly smaller rebound deformation of soil under unloading conditions, previous numerical calculation methods need to be improved and adapted to the soil deformation characteristics under unloading. Based on the above background, cyclic loading and unloading tests were carried out to study the deformation characteristics of soil under different loading levels, stress history, and unloading levels. Secondly, a unified modulus calculation model was established, especially for the unloading modulus, which considers the unloading stress history and current unloading stress level, and can provide the value of soil modulus in different states. The relationship between the unloading rebound modulus Esc and the rebound modulus Ec0 used in the numerical simulation was studied. Finally, a set of numerical calculation and analysis methods for shallow tunnel deformation caused by overlying soil excavation based on its rebounding characteristics is proposed. The rationality of the method is verified by two examples, and is applied to a practical project.