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Impact of faults and fault damage zones on large open pit slopes

University of British Columbia

The demand for metals combined with diminishing near surface resources has prompted the increasing development of complex and unprecedented open pit designs to recover deeper resources. These designs include pushback extensions, intentional over-steepening of toes, or the transition to underground retreat or mass mining methods. While past designs rarely involved pit depths exceeding 500 m, steeper and deeper designs approaching or exceeding 1000 m are now considered. Experiences with large open pits demonstrate that complex failure mechanisms occur with higher propensity within these slopes. New technologies used to monitor slope displacement, such as radar interferometry, along with increased real-time data processing have given engineers more data and faster tools to investigate the fundamental rock mechanics that occur within large slopes. Radar allows for the collection of large amounts of real-time data with millimeter precision. Emphasis is given in this thesis to the use of radar monitoring in resolving displacements in proximity to fault damage zones. Research was conducted to develop and execute a first of its kind 3-D radar experiment involving the simultaneous deployment of two radar systems. This experiment demonstrates that valuable knowledge, in the form of a 3-D displacement map, was used to resolve the influence of large fault zones in promoting complex slope deformation kinematics and failure mechanisms. In parallel, numerical modelling continues to develop as a key tool in understanding deep-seated rock slope deformation mechanisms. Research was conducted to investigate the characterization and representation of key fault properties within sensitivity analyses used to provide guidance on the impact of simplification of these complex structures. Representative geometries and input parameters based on case studies were used to show the influence of fault location, orientation and complexity, on stress heterogeneity created by the interaction between faults and deepening large open pits, as well as the transition to underground mass mining. These interactions can create zones of plastic shear strain or extensional strain damage not typically accounted for in most stability analyses. The inclusion of stress heterogeneity and subsequent rock mass damage is shown to modify the observed mechanisms of slope movement and allow previously unviable kinematics to develop.

Text

2017-03-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/61064

Geological Engineering

University of British Columbia

UBCV

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