Study on support time in double-shield TBM tunnel based on self-compacting concrete backfilling material

Double-shield tunnel boring machine (TBM) typically supports surrounding rock structures using precast lining segments, pea-gravel backfilling and grouting, which can provide full play for the self-bearing capacity of surrounding rock. However, the risk of TBM jamming is increased by a lack of timely support. We propose a support method using self-compacting concrete backfilling material (SCCBM) instead of pea-gravel backfilling and grouting. In this paper, based on simulations of a TBM construction process, the support time and mechanical properties of the SCCBM are analysed. The deformation characteristics of surrounding rock are simulated using the viscoplastic creep model based on the internal variable thermodynamics theory. Creep parameters are obtained through the inversion analysis of displacement data collected at a construction site. The age-hardening process of SCCBM is simulated using the Mohr–Coulomb criterion, whose mechanical parameters change over time. Surrounding rock deformation, support system stress, yield region, surrounding rock stability, and the effects of the age-hardening rate of SCCBM are analysed. Additionally, the optimal supporting time is determined by comprehensively analysing surrounding rock deformation and supporting system stress. Overall, backfilling SCCBM with an optimal supporting time can not only reduce the deformation of surrounding rock and risk of TBM jamming, but also enhance the stability of surrounding rock.