Exploring the time-dependent behaviors of the rock mass roof of tunnels in open underground spaces of coal mines through numerical investigation

The stability of rock mass roofs in open underground spaces of coal mines in Iran is a critical concern, as it can have significant implications for mine safety and productivity. The rock mass roofs are prone to degradation and failure due to various factors, including mining-induced stress, water infiltration, and mechanical damage. However, there needs to be more understanding of the time-dependent behaviors of these rock mass roofs. This study aims to investigate the time-dependent behaviors of rock mass roofs in tunnels of open underground spaces of coal mines in Iran using numerical simulations. A 3D numerical model was developed using finite element modeling. The model was validated using field measurements and laboratory tests. The study revealed that the rock mass roof exhibits significant time-dependent behavior in response to mining-induced stress, water infiltration, and mechanical damage. The results show that the rock mass roof deforms significantly over time, increasing the risk of instability and collapse. The study also investigated the influence of bedding planes and roof support on time-dependent behavior, demonstrating the importance of considering these factors in numerical simulations. A novel constitutive model was developed to represent the strain-softening behavior, creep, and relaxation of rocks, as well as strength deterioration with accumulated viscous deformation. The study identified the critical factors contributing to this deformation and instability, including high-stress zones, water infiltration pathways, and mechanical damage. The findings provide valuable insights for developing effective monitoring and mitigation strategies to ensure the safety and productivity of coal mines in Iran.