Effect of Grain Size and Surface Roughness on the Normal Coefficient of Restitution of Single Grains

Abstract

The coefficient of restitution (COR) represents the fraction of pre-collision kinetic energy remained after the collision between two bodies. The COR parameter plays an important role in the discrete numerical analysis of granular flows or the design of protective barriers to reduce flow energy. This work investigated the COR for grain-block type impacts through comprehensive experiments using a custom-built impact loading apparatus. Glass balls of three different sizes were used as grains.The impact experiments were performed on three different types of materials as base blocks, namely brass, granite and rubber. Experiments on the brass block showed a decrease in COR values with increasing grain size. On the contrary, impacts on granite and rubber blocks showed an increase in COR values with increasing grain size. Additionally, the effect of surface roughness on the COR was investigated. It was revealed that the increase in surface roughness of either the grain or the block reduced the COR values due to the increased plastic deformations of surface asperities.

Assessing the effect of lithological setting, block characteristics and slope topography on the runout length of rockfalls in the Alps and on the island of La Réunion

“…Our analyses reveal a complex relation between block size and block shape with respect to the runout distance of deposited blocks with divergences between different lithological settings. Compared to other studies (Whitehouse and McSaveney, 1983;Jomelli and Francou, 2000;Sanders et al, 2009;Luckman, 2013a;Messenzehl and Dikau, 2017;Popescu et al, 2017) and with respect to our results we can neither confirm nor reject the theory of gravitational sorting (Figs. 7b and 8b) as we did not find a clear relationship between block size and runout distance.…”

“…The average slope inclinations of the talus cones lie between 28 and 36 • and thus within the range for such landforms (e.g. Pérez, 1989Pérez, , 1998Francou and Manté, 1990;Jomelli and Francou, 2000;Sanders et al, 2009;Luckman, 2013b, Popescu et al, 2017Volkwein et al, 2018). The mean slope inclination values for the talus cones of our study sites are for PF, the ZBT, GA and DTS 29, 32, 36 and 32 • , respectively.…”

“…Some studies have described the deposition of boulders on the talus cone as gravitational sorting, where larger blocks are deposited in the distal part and smaller blocks on the upper part of the talus slope (e.g. Statham, 1973;White, 1981;Whitehouse and Mc-Saveney, 1983;Kotarba and Strömquist, 1984;Jomelli and Francou, 2000;Sanders et al, 2009;Messenzehl and Dikau, 2017;Popescu et al, 2017;Kenner, 2019). The gravitational sorting of the blocks on the slope is a key factor for the roughness component of talus slopes and thus for the runout length of following rockfall events (Hungr and Evans, 1988), indicating a potential feedback loop in the formation of talus landforms.…”

3D DEM analysis of analogue proppant–fractured rock system interaction

“…Particularly, the impact calibration parameters (i.e. the contact properties between the impactor and the base) were meticulously selected based on impact experiments and tribological micromechanical-based tests (Sandeep et al 2020(Sandeep et al , 2021Senetakis 2018, 2019).…”

“…The collision (or impact) behaviour of solid objects, apart from its direct interest in the study of hydraulic fracturing problems, is also encountered in various industrial and natural systems, such as flow behaviour of powders and grains and pharmaceutical applications (Aryaei et al 2010;Yu and Tafti 2016;Stronge 2018;Li et al 2019), or granular flows and interactions of landslide materials with protective barriers (Iverson 1997;Clelland and Hrenya 2002;Moriguchi et al 2009;Teufelsbauer et al 2011;Cui et al 2018;Hu et al 2018;Jiang et al 2018;Li and Zhao 2018;Shen et al 2018;Tan et al 2021;Yang et al 2021). Within this context, many studies have attempted to provide fundamental insights into the impact problem of particle against block systems through experimental (Marinack et al 2013;Patil and Higgs 2017;Tang et al 2019;Wang et al 2020b;Sandeep et al 2020Sandeep et al , 2021 and numerical simulations (Aryaei et al 2010;Jiang et al 2019;Tang et al 2019;Wang et al 2020b;Calvetti et al 2017;Marzulli et al 2020). An example of recent numerical simulation works highlighting the impact or collision behaviour of granular materials may refer in the study by Shen et al (2019).…”