A prediction method for long-term surface subsidence considering the mining-induced stratum creep effect and its application

Considering the rock creep effect can effectively improve the prediction accuracy of surface subsidence in goafs, which is particularly important for determining construction timing and ensuring the safe operation of surface structures. On basis of the time-dependent deformation characteristics of the overlying strata in mining areas, a nonlinear viscoelastic‒plastic (NVEP) model for accurately describing the three-stage creep behavior of rocks was established. The three-dimensional creep constitutive equations of this model were derived, and a secondary development of the creep model was implemented on the FLAC^3D numerical simulation platform. A creep parameter inversion method for overlying strata in goaf areas was proposed by combining creep simulation analysis with a genetic algorithm. A specific project was selected as a case study, and the creep model and its related parameters were subsequently used to predict the long-term surface settlement behavior, providing a scientific basis for determining the appropriate construction timing for the surface railway in the goaf area of the region. The numerical simulation results indicate that the surface subsidence exhibits an exponential decay trend, which can be divided into three distinct stages: an initial rapid settlement phase (0-2 years), a transitional phase (2-3 years), and a long-term stabilization phase (beyond 4 years). On the basis of the railway construction specifications and the results of the numerical simulation analysis, the feasibility of constructing a railway on the goaf surface is assessed. The findings indicate that railway construction above the goaf in this area should be postponed for at least five years after the cessation of mining activities.