Excavation compensation and bolt support for a deep mine drift

Abstract

To overcome large deformation of deep phosphate rock roadways and pillar damage, a new type of constant-resistance large-deformation negative Poisson's ratio (NPR) bolt that can withstand a high pre-stress of at least 130 KN was developed. In the conducted tests, the amount of deformation was 200–2000 mm, the breaking force reached 350 KN, and a high constant-resistance pre-stress was maintained during the deformation process. A stress compensation theory of phosphate rock excavation based on NPR bolts is proposed together with a balance system for bolt compensation of the time-space effect and high NPR pre-stress. Traditional split-set rock bolts are unable to maintain the stability of roadway roofs and pillars. To verify the support effect of the proposed bolt, field tests were conducted using both the proposed NPR bolts and split-set rock bolts as support systems on the same mining face. In addition, the stress compensation mechanism of roadway mining was simulated using the particle flow code in three dimensions (PFC3D)-fast Lagrangian analysis of continua (FLAC3D) particle-flow coupling numerical model. On-site monitoring and numerical simulations showed that the NPR excavation compensation support scheme effectively improves the stress state of the bolts and reduces the deformation of the surrounding rock. Compared to the original support scheme, the final deformation of the surrounding rock was reduced by approximately 70%. These results significantly contribute to domestic and foreign research on phosphate-rock NPR compensation support technology, theoretical systems, and engineering practices, and further promote technological innovation in the phosphate rock mining industry.