Gravity flow and fragmentation modeling in Block Caving

Abstract

In block caving, the behavior of gravity flow is fundamental in mine design and pla nning. However, the great number of variables that influence this large scale phenomenon are difficult to study directly in the field. There are variables that depend on the rock type, stress field and the dynamics of the operation itself through the cavin g progress and draw policies, which will define the performance of the method. This large number of factors have been studied to different degrees in some cases with lack of knowledge of their real influence. Thus, this work has developed various studies i n block caving related to the secondary fragmentation, the migration of fine material and the stress in the draw column, in order to update the state of the art and propose a flow model that integrates a greater number of key parameters. The structure of this thesis was divided into 5 stages. First, the effect of different rock types was analyzed in a secondary fragmentation model, and this model was compared with the what was found at the mine. Second, the study of fragmentation in the granular material w as complemented by analyzing the effect of the travel distance in fragmentation by abrasion. Third, an experimental work was carried out to analyze the induced stress by draw in a broken column. Fourth, a stress model was developed using a flow simulator b ased on cellular automata. Finally, a fragmentation model and a fine migration model were incorporated in the previous flow simulator. These models included the rock size in the flow function. In rock fragmentation, the described stages allowed a secondar y fragmentation model to be calibrated based on different rock types. Additionally, a correction to the secondary fragmentation model is proposed, including a greater amount of fine material generated as a function of the travel distance. These fragmentati on studies incorporate the rock strength and induced vertical stress. The proposed vertical stress models the stress generated in the extraction zones, which was calibrated and validated on an experimental scale. Finally, the stress and fragmentation model s are included in the flow simulator which used the mean rock size as a key variable. The mean rock size is fragmented during draw and influences the flow probability inversely. The present work allows different key aspects present in the broken column in block caving to be linked, simulating the gravity flow with greater precision and proximity to the real phenomenon. Furthermore, the advantage of incorporating the studies carried out in a gravity flow simulator based on cellular automata is that differe nt aspects and parameters can be assimilated with good precision and in a reasonably short simulation for the problem scale.