Stability analysis of surrounding rock of deep underground engineering considering fluid–solid coupling effect

When constructing underground engineering projects within water-rich strata, the adverse effects of high ground stress, high water pressure and excavation disturbance are significant, and can easily lead to disasters such as instability of the surrounding rock. There is an urgent need to study the stability of surrounding rock in deep underground engineering works under fluid–solid coupling. This study develops a three-dimensional finite-difference-based fluid–solid coupled non-linear model incorporating initial pore water pressure and excavation progress. The evolution of the multi-field response of surrounding rock during excavation under diverse pressure conditions is studied. The findings demonstrate that as initial pore water pressure rises, the plastic zone progressively extends deeper into the surrounding rock, while the deformation of the surrounding rock, the seepage velocity and the influence range of groundwater seepage all increase. The maximum seepage velocity of groundwater reaches 5.1 × 10−6 m/s. When excavation advances to 2 m, the stress concentration area is mainly concentrated in the corner area where the sidewall and the vault intersect and the corner area where the sidewall and the arch bottom intersect. When the footage is 4 m, the deformation of surrounding rock increases significantly. The vault displacement surges abruptly from 1.7 to 8.0 cm, while the arch bottom displacement rises linearly from 2 to 7 cm. The research results can provide some reference and guidance for similar underground engineering.