Step-Path method — impact of defect occurrence, cut-off and length on shear strength in rock slopes

Baczynski, Norbert

doi:10.36487/acg_rep/1604_14_baczynski

Cited by 2 publications

(3 citation statements)

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“…This paper shows that when bedding planes and subvertical joints are considered, the Step-Path estimated shear strengths for some rock types may be as high as 30-45% less than corresponding Hoek-Brown strength. This observation is similar to the writer's previous conclusions for other slope examples (Baczynski 2016). However, the average shear strength difference between weighted-average (i.e.…”

Section: Resultssupporting

confidence: 91%

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Simplified Step-Path method for rock slopes

Baczynski¹

2016

Proceedings of the First Asia Pacific Slope Stability in Mining Conference

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Strength of most rock masses is anisotropic. This means that strength is often not uniform in all directions but depends on layering and structural fabric of the rocks. Three components of strength are rock mass, geological defects and intact rock or rock mass 'bridges' between defects. The Hoek-Brown criterion applies to those segments of failure path that are not co-aligned with dominant defect orientations. Conversely, the Hoek-Brown criterion is less representative where the failure path is co-aligned with such fabric. In the latter case, strength is better estimated by the Step-Path method. This approach requires slope face mapping data for several input parameters; drill core does not provide the necessary data. Conventional Step-Path methods use Monte-Carlo simulation of large numbers (> 10,000) of paths (Baczynski 2000). Any statistical model (normal, lognormal, exponential) can be considered for input parameters; many are lognormally distributed. A less rigorous Simplified Step-Path method is described in this paper. However, this approach has a limitation; statistical variability for all inputs is approximated by normal distributions. The Rosenblueth method of statistical moments, and Sampling Theory, are used to develop statistical strength models for any user-nominated Step-Path traverse length. Analysis is Excel spreadsheet based. Case study examples are presented. Step-Path computed strength may be 30 to 45% less than Hoek-Brown values. This strength reduction significantly decreases Factors of Safety and increases stability risks for rock slopes.

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Section: Resultssupporting

confidence: 91%

“…Rock masses exhibit directional strength due to co-alignment of some geological defect sets with specific directions of shearing. The Step-Path method provides a statistically-based approach for estimating shear strength along defect-controlled failure paths through rock masses (Baczynski 2000(Baczynski , 2016.…”

Section: Introductionmentioning

confidence: 99%

Simplified Step-Path method for rock slopes

Baczynski¹

2016

Proceedings of the First Asia Pacific Slope Stability in Mining Conference

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“…The simplified Step-Path method was used to assess an Asian multi-seam coal mining project during 2010 (Baczynski 2016). Several existing 50 to 200 m deep open pits occur within a 30 by 30 km lease area.…”

Section: Case Studymentioning

confidence: 99%

Rock slope stability risks

Baczynski¹

2016

Proceedings of the First Asia Pacific Slope Stability in Mining Conference

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The methodology and factors that impact on rock mass slope stability risks are data collection, processing, reliability and the partitioning of data into domains. This paper discusses the development of statistical models for geological defect and rock mass attributes. Kinematic stability analyses are mandatory to identify slope failure modes. The Hoek-Brown method is commonly used to assess rock mass strength, but sometimes overestimates the strength. The author advocates a Step-Path method, where directional rock mass strength is considered. Sampling Theory relationship between mapping-window sizes, lengths of failure paths through slopes and strength variability is described in this paper. The Rosenblueth matrix is used to develop statistical strength parameters and assess stability risks. An equation is provided for the combining of stability risks computed for several failure modes in different slopes. In the presented case study, the Step-Path strength yields a 30% lower Factor of Safety than the Hoek-Brown strength. Sampling Theory adjustments result in a five-fold decrease in the statistical spread of Factors of Safety and a significant decrease in the estimated stability risks. https://papers.acg.uwa.edu.au/p/1604_30_Baczynski/ Rock slope stability risks NRP Baczynski 470 APSSIM 2016,

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Step-Path method — impact of defect occurrence, cut-off and length on shear strength in rock slopes

Cited by 2 publications

References 3 publications

Simplified Step-Path method for rock slopes

Simplified Step-Path method for rock slopes

Rock slope stability risks

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