Numerical modeling of entry position design: A field case

Abstract

In coal mining, roof collapse and support body failure during entry excavation are a common problem. During excavation, entry positions may be subjected to separation, shear-slip, support body failure, and roof collapse. Weak coal-rock interfaces allow for shear-slip between layers, causing anchor bolts and cables to fail. Six entry position models are created to evaluate the failure process and determine the best entry position. Results indicate that roof rocks experience bending and shear-slip along the coal-rock interface. Nearby mining activity causes asymmetric deformation of the entry and shear-slip at the roof corners. When anchor cables and bolts in the roof are insufficient to limit separation and shear-slip, support bodies are subjected to tension, shear, and bending. Once the support body fractures, the entry roof experiences progressive deformation resulting in collapse. We determine the optimal entry position in which shear-slip and residual coal are minimized.