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O'Neill, Shane; Eberhardt, Erik Brian, 1969-; Beckie, Roger D.

Initiation of, and mechanisms controlling mid-slope, multi-bench failures are poorly understood. Failures are assumed to be controlled by daylighting discontinuities exposed in the slope toe or driven by slope height and gravity loading relative to rock mass strength, thus encompassing the entire slope. This understanding does not explain why there are multi-bench failures in the mid to upper areas of the slope, years after being mined. We present the hypothesis and empirical evidence suggesting mid-slope, multi-bench failures are driven by transient pore pressures, related to seasonal precipitation, resulting in progressive failure. 364 open-pit slope failure case studies were analyzed. Useful slope failure characteristics identified were failure duration, overall angle, failure location, rupture depth, trigger, failure mode, and Bell’s (1966) modified stability number, a proxy for rock mass shear strength. The data shows that actively mined weak rock slopes are more likely to fail in the lower part within 1 to 2 years of mining, whereas moderately strong rock slopes tend to fail in the mid to upper slope after more than 7 years of mining (increasing up to 9 years for strong rock). Transient pore-pressure pulses related to seasonal precipitation are the common factor, with stronger rock masses requiring more transient pore-pressure pulses to progressively weaken the slope until failure. [Original files updated following post-peer review revisions and two addenda files added on 2024-06-26.]

Article

eng

Vancouver : University of British Columbia Library

10.14288/1.0435742

Science, Faculty of; Earth, Ocean and Atmospheric Sciences, Department of

Database used to support paper entitled "Empirical Analysis of Mid-Slope, Multi-Bench Open Pit Slope Failures" submitted to Canadian Geotechnical Journal, in August 2023

Faculty; Graduate

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