A study of gravity flow principles of sublevel caving method in dipping narrow veins

摘要

The loss and dilution of ore by sublevel caving mining method is influenced by gravity flow principles of caved granular materials (rocks). Gravity flow of broken rock (muck) in dipping narrow veins is complex. By combined use of dimensional analysis and similitude studies in physical modelling coupled with numerical simulation, this paper reports results of a study of gravity flow of muck in dipping narrow veins on the basis of granular material kinematics and dynamics. By similitude material testing, the paper analyzed the forms of granular motion during the extraction process, studies the impacts of parameters including model thickness and wall roughness on the form and size of the extraction zone. The test results reveal that depending on wall inclination (dip), the axis of granular flow shifts, and the extraction zone is intrusively asymmetric. Also, the greater the distance from the hanging wall of the model and the smoother the wall roughness, the easier the granular ore flows and the greater the volume of the extraction zone. By using PFC2D modelling, the mechanical mechanism of granular ore flow is analyzed. The model results show that under conditions of dipping narrow veins, the formation and development of the extraction zone are mainly controlled by two mechanisms, namely: the disintegration of the stress arch and the erosion of granular particles. Finally, the study established a mechanistic model of granular flow in dipping narrow veins in sublevel caving mining conditions. By applying the Levenberg-Marquardt nonlinear optimization method the paper defined optimal model parameter values under different experimental conditions.