Discrete element modelling of deformation and damage of a roadway driven along an unstable goaf - A case study

Roadways driven alongside a previously extracted longwall panel (goaf) are a common situation in underground coal mining. The unstable goaf can have a significant detrimental impact on the stability of the roadway. This paper presents a combined SRM-UDEC Trigon numerical approach to investigate the failure mechanism of a roadway driven alongside an unstable goaf. The synthetic rock mass (SRM) method is used to derive the rock mass properties and the newly developed UDEC Trigon approach is used for simulating brittle fracture and consequent roadway damage. The results indicate that the roadway suffers asymmetric damage characterized by a major rib convexity, a severe floor heave and a relatively stable roof with limited fracturing. This failure mechanism is consistent with field observations. A quantitative evaluation of the damage around the roadway indicates that shear failure plays a major role in the roadway damage. Our study suggests that the proposed combination of SRM and the UDEC Trigon is well suited to the evaluation of failure mechanisms around underground coal mine excavations.