Preprints
https://doi.org/10.5194/esurf-2021-17
https://doi.org/10.5194/esurf-2021-17

  09 Mar 2021

09 Mar 2021

Review status: a revised version of this preprint is currently under review for the journal ESurf.

Breaking down chipping and fragmentation in sediment transport: the control of material strength

Sophie Bodek1 and Douglas J. Jerolmack2,3 Sophie Bodek and Douglas J. Jerolmack
  • 1Department of Earth Sciences, University of Delaware, Newark, Delaware, USA
  • 2Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
  • 3Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, USA

Abstract. As rocks are transported, they primarily undergo two breakdown mechanisms: chipping and fragmentation. Chipping occurs at relatively low collision energies typical of bed-load transport, and involves shallow cracking; this process rounds river pebbles in a universal manner. Fragmentation involves catastrophic breakup by fracture growth in the bulk – a response that occurs at high collision energies such as rock falls – and produces angular shards. Despite its geophysical significance, the transition from chipping to fragmentation is not well studied. Indeed, most models implicitly assume that impact erosion of pebbles and bedrock is governed by fragmentation rather than chipping. Here we experimentally delineate the boundary between chipping and fragmentation by examining the mass and shape evolution of concrete particles in a rotating drum. Attrition rate should be a function of both impact energy and material strength; here we keep the former constant, while systematically varying the latter. For sufficiently strong particles, chipping occurred and was characterized by the following: daughter products were significantly smaller than the parent; attrition rate was independent of material strength; and particles experienced monotonic rounding toward a spherical shape. As strength decreased, fragmentation became more significant: mass of daughter products became larger and more varied; attrition rate was inversely proportional to material strength; and shape evolution fluctuated and became non monotonic. Our results validate a previously proposed probabilistic model for impact attrition, and indicate that bedrock erosion models predicated on fragmentation failure need to be revisited. We suggest that the shape of natural pebbles may be utilized to deduce the breakdown mechanism, and infer past transport environments.

Sophie Bodek and Douglas J. Jerolmack

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-17', Alexander Beer, 14 Apr 2021
  • RC2: 'Comment on esurf-2021-17', Anonymous Referee #2, 23 Apr 2021
  • AC1: 'Comment on esurf-2021-17', Sophie Bodek, 20 Jun 2021

Sophie Bodek and Douglas J. Jerolmack

Data sets

Particle Shape Evolution from Rotating Drum Experiments Sophie Bodek and Douglas Jerolmack https://doi.org/10.6084/m9.figshare.14069105

Sophie Bodek and Douglas J. Jerolmack

Viewed

Total article views: 698 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
518 168 12 698 8 6
  • HTML: 518
  • PDF: 168
  • XML: 12
  • Total: 698
  • BibTeX: 8
  • EndNote: 6
Views and downloads (calculated since 09 Mar 2021)
Cumulative views and downloads (calculated since 09 Mar 2021)

Viewed (geographical distribution)

Total article views: 613 (including HTML, PDF, and XML) Thereof 613 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 20 Oct 2021
Download
Short summary
As rocks are transported, they undergo two attrition mechanisms: chipping, shallow cracking at low collision energies, and fragmentation, significant fracture growth from high-energy impacts. We examine the mass and shape evolution of concrete particles in a rotating drum to experimentally delineate the boundary between chipping and fragmentation. By connecting the mechanics of these attrition processes to resulting shape evolution, we can use particle shape to infer past transport conditions.