Mechanical Model for Calculating Surface Movement Related to Open-Pit and Underground Caving Combined Mining

Surface movement under the combined mining of open-pit and underground caving is main problem affecting safe efficient mining. Taking Dahongshan Iron Mine as an example, a mechanical model for calculating surface range was established to reveal mechanism. The topography, zone, gravel filling zone depth were considered, principal stress calculated. Based on model, relationship between subsidence angle cracking definition supplemented: measured from horizontal moving boundary line, straight line with zero displacement edge deepest extraction level largest range. A trial calculation method proposed: by presetting different angles, corresponding maximum prone calculated found real angle. 60°, consistent observed 64° in Mine, which verifies reliability model.