Preliminary expansion of the Modified Ritchie Criterion: an empirical approach to determining minimum bench widths for rockfall catchment

Authors: Warren, S; McNabb, JC; Meyer, BJ; Potter, JJ; Sbai, S; Reasoner, AE; Ryan, T

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DOI https://doi.org/10.36487/ACG_repo/2535_04

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Warren, S, McNabb, JC, Meyer, BJ, Potter, JJ, Sbai, S, Reasoner, AE & Ryan, T 2025, 'Preliminary expansion of the Modified Ritchie Criterion: an empirical approach to determining minimum bench widths for rockfall catchment', in JJ Potter & J Wesseloo (eds), SSIM 2025: Fourth International Slope Stability in Mining Conference, Australian Centre for Geomechanics, Perth, https://doi.org/10.36487/ACG_repo/2535_04

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Abstract:
The Modified Ritchie Criterion (MRC) is a widely utilised tool used for catch bench design in the mining industry. The MRC, based on Ritchie’s 1960s highway rockfall catchment studies and later adapted for mining applications,defines the minimum required catch bench width (CBW) as CBW = 0.2(bench height) + 4.5 m. While the criterion has been utilised successfully for decades, experience and research has shown that rockfall rollout is a complex problem, and the determination of the required minimum rockfall catch bench width is a function of more variables than bench height alone. This paper quantifies the effect of factors such as rock size and catch bench angleon rockfall rollout distance using multivariate regression on a rockfall dataset developed by the Oregon Department of Transportation in 2001.Results indicate that rockfall rollout distance and catch bench performance are functions of multiple variables, including bench height, bench face angle, rock size, and catch bench angle.Several empirical regressions are presented for determining catch bench widths with 90% rockfall retention – a commonly applied performance metric in the mining industry. The regressions are used to propose a preliminary datasupported expansion of the Modified Ritchie Criterion (termed EMRC). This potentialexpansion accounts for variations in bench face angle, reducing minimum catch bench width for bench face angles steeper than 65°, and increasing minimum catch bench width for bench face angles shallower than 65°.

Keywords: rockfall, rollout, runout, catch bench design, slope design

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