Theoretical model and numerical simulation research on minimum overburden thickness of TBM excavation based on surrounding rock arching theory

Abstract

Based on the surrounding rock arching and hinge-less arch structure theories, a theoretical formula for the minimum overburden thickness was derived. By substituting different mechanical parameters of multiple tunnels at home and abroad into this formula, minimum self-supporting arch formulas under different surrounding rock classes were obtained. Based on the actual engineering case of a dual-mode shield tunnel, a numerical model for the tunnel boring machine excavation mode was established to verify the theoretical formulas. Next, three surrounding rock classes, four soil layer thickness gradients, and twelve overburden thickness gradients were designed, resulting in 144 models formed by the combination of the three factors. Uniform tests were conducted, and the pressure arch heights under different surrounding rock classes were obtained. The results show that in the theoretical formulas, the tunnel radius has a linear positive correlation with the pressure arch height, while the tunnel depth has a linear positive correlation with the square of the pressure arch height. According to numerical simulation results, the pressure arch height increases with the increase of the overburden thickness and then tends toward a critical value of twice the tunnel diameter. Finally, the results of the numerical model are in good agreement with those calculated using the theoretical formulas, verifying the rationality of the established theoretical formulas.

Keywords

minimum overburden thickness / tunnel boring machine (TBM) / pressure arch / numerical simulation / self-supporting arch

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Funding

National Natural Science Foundation of China(52478426)

Natural Science Foundation of Hunan Province(2024JJ5428)