Ground movement due to longwall mining in high relief areas in New South Wales, Australia

Abstract

Abstract The theoretical pattern of ground movement observed in flat terrains was modified by surface topography and geological structures. In high relief areas, e.g. creeks and gullies, the observed pattern of movement was asymmetrical about the centre of the extraction panel. The lateral movement of both sides of the valley caused large compressive strains and a hump at the creek bed. The strains were three–four times those normally observed in flat or fairly gentle topographies. The hump was due to the rock mass in the creek bed being pushed up by the lateral forces from the valley sides. A major geological fault caused both sides of the valley to move laterally away from the fault plane. The magnitude of the maximum horizontal movement was as large as 40% of the observed vertical movement. Outside the goaf, the horizontal movements were generally larger than the corresponding vertical movements. However, the horizontal movements outside the goaf appeared to be rigid body type movements with small deformations which may only have insignificant surface consequences.