The slope of dry granular materials surface is generally curved

• Main Authors: Abdullah, M. (Author), Akbar, F. (Author), Amalia, N. (Author), Rahmayanti, H.D (Author), Yuliza, E. (Author)
• Format: Article
• Language: English
• Published: Springer Science and Business Media Deutschland GmbH 2022
• Subjects: Angle of repose; Critical grain size; Critical grain sizes; Critical size; Curved slope; Curved slopes; 'Dry' [; Friction; Grain size and shape; Granular heap; Granular materials; Janssen; Janssen effect; Landforms; Material's surface; Sand dune; Sand dunes
• Online Access: View Fulltext in Publisher

 A closer inspection shows that the granular heap slopes are not truly straight. Instead, more often they have convex shapes. Here, we show that the granular heap slopes, in general, are convex (curved downwards). This prediction is in accordance with the results of measurements on 10 types of granular heaps. The model answers why the surfaces of granular heaps, including desert sand dunes, are more often convex than straight. We also predict the existence of a critical grain size, where the repose angle is 90° at the critical size and is undefined if the grain size is less than the critical size. The critical grain size estimated by the present model is consistent with the experimental results of previous researchers. This model also advocates the simultaneous estimation of the coefficient of friction on the grain and type of packing in the heap. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.