Controls on the rates and products of particle attrition by bed-load collisions
Abstract
River rocks round through the process of impact attrition, whereby energetic collisions during bed-load transport induce chipping of the grain surface. This process is also important for bedrock erosion. Although previous work has shown that impact energy, lithology, and shape are controlling factors for attrition rates, the functional dependence among these quantities is not settled. Here we examine these factors using a double-pendulum apparatus that generates controlled collisions between two grains under conditions relevant for bed-load transport. We also determine the grain size distributions (GSDs) of the attrition products. Two experimental results appear to support previous treatments of impact erosion as brittle fracture: (i) mass loss is proportional to kinetic energy, and this proportionality is a function of previously identified material properties; and (ii) attrition-product GSDs are well described by a Weibull distribution. Chipping results from the development of shallow and surface-parallel cracks, a process that is distinct from bulk fragmentation that occurs at higher energies. We suggest that Hertzian fracture is the dominant mechanism of impact attrition for bed-load transport. We also identify an initial phase of rapid mass loss in which attrition is independent of energy and material properties; this is a shape effect associated with removal of very sharp corners. The apparent universality of both mass loss curves and attrition-product GSDs requires further investigation. Nonetheless, these findings are useful for interpreting the contribution of in-stream attrition to downstream fining and the production of sand resulting from bed-load transport of river pebbles.
Additional Information
© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 19 October 2020 – Discussion started: 31 October 2020; Revised: 20 May 2021 – Accepted: 8 June 2021 – Published: 23 July 2021. We thank Gerard Salter and Raleigh Martin for their assistance in the laboratory. Thank you to Leonard Sklar for allowing use of equipment and lab space for material property measurements and Sirui Ma for hardness measurements. We thank the editor, Francois Metivier, and reviewers, namely Stephanie Deboeuf, Sebastien Carretier, and Jeffrey Prancevic, for their time and feedback, which greatly improved this paper. This research has been supported by the National Science Foundation, Directorate for Geosciences (grant no. NSF EAR 1331841). Data availability: All data used for plots in this paper are deposited on figshare, a publicly available and open repository: https://doi.org/10.6084/m9.figshare.13169498.v1 (Litwin Miller, 2020). Author contributions: KLM led the research, performed data analysis, and wrote the paper. DJJ supervised the research, assisted in data interpretation, and edited the paper. The authors declare that they have no conflict of interest. Review statement: This paper was edited by Francois Metivier and reviewed by Stephanie Deboeuf, Sebastien Carretier, and Jeffrey P. Prancevic.Attached Files
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Additional details
- Eprint ID
- 110356
- Resolver ID
- CaltechAUTHORS:20210821-152151168
- EAR-1331841
- NSF
- Created
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2021-08-21Created from EPrint's datestamp field
- Updated
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2021-08-21Created from EPrint's last_modified field