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UBC Theses and Dissertations

Characterisation of block cave mining secondary fragmentation Liu, Yubo


Block cave mining is a widely employed mining method around the world due to its low operating cost. One of the key factors that affects block caving mine’s productivity is fragmentation; accordingly, significant efforts have been made and are currently being made to study fragmentation processes, including the use of numerical modelling and remote sensing techniques. It is desirable to develop fragmentation models that could be used to provide reliable estimates of the range and distribution of the sizes of the rock blocks expected to be induced by caving. In the context of block and panel cave mining, fragmentation processes are characterised as: i) In-situ (natural) Fragmentation: in-situ blocks that are naturally present within the rock mass before any mining activity takes place. They are defined by the pre-existing discontinuities. ii) Primary Fragmentation: blocks that separates from the cave back as the undercut is mined and caving is initiated. iii) Secondary Fragmentation: fragmentation that occurs as the blocks move down through the ore column to the drawpoints. The main goal of this thesis is to attempt to establish a relationship between in-situ fragmentation and secondary fragmentation. This is achieved by: i) Measuring secondary fragmentation observed at the drawpoints. Digital image processing is employed in this process, using WipFrag (WipWare, 2014) and PortaMetrics (MotionMetrics, 2015). ii) Using Discrete Fracture Networks (DFN) to generate in-situ fragmentation curves based on data mapped from boreholes and drifts. The code FracMan (Golder, 2014) is used to generate the DFN model and the fragmentation curves. Additionally, the height of draw data from code PCBC (Systems, 2015) is used to establish a relationship between modelled in-situ fragmentation and measured secondary fragmentation. iii) This research is considered to benefit the assessment of block caving fragmentation specifically the estimate of oversizes (hang-ups) at draw columns. Also as a part of the on-going project Cave-to-Mill (Nadolski, et al., 2015) conducted at UBC Mining, this research will feed into the further analysis of Cave - to - Mill study.

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