Study on Instability Mechanism of Extraction Structure under Undercut Space Based on Thin Plate Theory in Block Caving Method

The instability of extraction structure under the undercut space in block caving stope presents specific characteristics: rib spalling and floor heave ore-loading roadway collapse major apexes. In order to study stress displacement evolution law reveal mechanism structure, numerical simulation model was established using finite difference software FLAC3D. According postundercutting strategy Tongkuangyu Mine China, formed first process, then level divided into eight units for excavation step by step. after each undercutting were monitored analyzed. Based on thin plate theory, change deflection deformation revealed. research results show that, action high horizontal tectonic vertical stress, produces upward bending during caving. tension concentration gradually appears side wall tip apexes; with increase area, degree tensile becomes strong; when strength rock mass is exceeded, instability. It necessary make overlying ore as soon possible undercutting, which beneficial release space.