Influence of bottom roughness and ambient pressure conditions on the emplacement of experimental dam-break granular flows Montserrat, S. Ordonez, L. Tamburrino, A. /Roche, Olivier Dam-break Granular flows Pore pressure Ambient pressure Fluidization Substrate roughness Geophysical granular flows occur at the surface of the Earth and other planets with reduced atmospheric pressure. In this paper, we investigate the run-out of dam-break flows of particle-air mixtures with fine (d = 75 mu m) or coarse (d = 150 mu m) grains in a flume with different bottom roughness (delta) and vacuum degrees (P*). Our results reveal an increase of the flow run-out as d/delta decreases for fine d = 75 mu m-particles, and run-out decreases with the dimensionless ambient pressure (P*) for a given d/delta. In contrast, the run-out for coarser d = 150 mu m-particles, is almost invariant respect to P* and d/delta. These results show that autofluidization of fine-grained flows demonstrated by earlier works at ambient pressure also occurs at reduced pressure though being less efficient. Hence, autofluidization is a mechanism, among others, to explain long run-out of geophysical flows in different environments. 2021 text https://www.documentation.ird.fr/hor/fdi:010081462 fdi:010081462 Montserrat S., Ordonez L., Tamburrino A., Roche Olivier. Influence of bottom roughness and ambient pressure conditions on the emplacement of experimental dam-break granular flows. 2021, 23 (3), 57 [8 ] EN