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

• Published in: Shock and vibration 2021, Vol.2021 (1)
• Main Authors: Xia, Zhi-Yuan, Tan, Zhuo-Ying
• Format: Article
• Language: English
• Subjects: Analysis; Apexes; Caving; Collapse; Crack propagation; Deformation; Finite difference method; Laboratories; Laws, regulations and rules; Mathematical models; Methods; Mining; Numerical analysis; Onsite; Plate theory; Roads; Roads & highways; Simulation; Simulation methods; Spalling; Stress concentration; Stress state; Structural stability; Tectonics; Tensile strength; Tensile stress; Thin plates
• ISSN: 1070-9622; 1875-9203
• DOI: 10.1155/2021/5548213

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