Mining-induced ground movement in tectonic stress metal mines: a case study

In-situ monitoring data for horizontal and vertical displacements in the Chenchao Iron Mine were collected over an eight-year period. The results were analysed to investigate ground movements induced by underground mining: large-scale ground deformation was found in mining areas of the footwall, and the angle of ground movement in the footwall was lower (by approximately 10°–14°) than that in the hanging wall. This was attributed to the combined response to the geomechanical setting of the orebody, many groups of structure planes, and in-situ stresses under the area of underground mining in the footwall, which generates ground movement by an “onlap effect”. When a fracture plane forms in a deep rock mass, then the mining-induced ground movement area is divided into: a toppling-sliding zone, a toppling zone, and a stability zone. Eventually, correction factors for the influence of the in-situ stress and major structure plane on the angle of ground movement in metal mines are given, as the “onlap hanging” structure exists in the footwall of the mine, which required a correction of between 10° and 15° in the northeastern part on the basis of the original angle of ground movement, and in the northern part, of between 5° and 10°.