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King, Matthew N.T.

University of British Columbia

In hard rock open pit mining environments the stability conditions of the bench are controlled by the structural discontinuities. Kinematic analyses of rigid blocks provide a prediction of the expected breakback following mining activities. In general, the observed breakback is steeper than that predicted using conventional kinematic analysis methods, which are known to have conservative assumptions such as ubiquity and full continuity of structures. However, this cannot be relied upon in all cases (i.e., exploration projects or mining projects not yet into construction) and design optimization or steepening does not occur until backed by empirical evidence. Utilizing a discrete fracture network (DFN) method involving polyhedral kinematics an attempt is made to see if the steeper observed designs can be predicted using structure that is stochastic and discontinuous. DFNs have limitations due to data uncertainty, in particular to the continuity of structures. Sensitivity assessments of the continuity of structures within a DFN are also investigated. Results of the DFN based kinematic analyses indicate steeper expected breakback angles compared to conventional kinematic analyses, however, the DFN results are inconsistent with the observed breakback conditions. Ultimately the DFN models failed to generate sufficient blocks to represent the actual breakback conditions. Future work is required particularly with regard to determining the validity of a DFN. Simple statistical assessments of DFNs only confirm that the DFN adheres to the input parameters such as orientation, continuity, and spacing. An additional check needs to be performed to assess if the spatial locations of the generated structures matches those of the observed structures. Additionally the potential of progressive failure of key blocks at the bench scale requires further analysis to determine its contribution to breakback of benches in a mining environment.

Text

2023-08-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85664

Mining Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/