Ground movement resulting from underground backfill mining in a nickel mine (Gansu Province, China)

Underground backfill mining is a complex and high-cost mining technique, whichwasdesignedtocontrolgroundpressureandprevent rockmass movementandground deformation.Unfortunately,theresults werenotalways asgoodasexpectedinpractice. This paper addresses a case of ground movement induced by backfill mining in a nickel mine, China.Combinedwithgeologicalinvestigationandgroundmonitoring,emphasiswasputon the analysis of ground movement and interpretation of the deformation and damage. The results showed that a ground depression was formed at the hanging wall surface of the mine. By the end of 2013, the maximum subsidence reached 2,404 mm and accompanied by the rapid development of ground fissures. The monitored ground movement corresponded well with the underground goaf and the distribution of the ground fissures. It also found that the seriously deformed and damaged tunnels were exactly located in the plane projection of the subsidence trough. In addition, this study suggested that the high-level in situ stresses strengthened the mechanical strength of the surrounding rock mass and affected the over- riding displacements in the wall rocks, thereby resulting in lower magnitude of vertical subsidence but greater expansion of horizontal deformation of the ground.