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Dimensionless critical shear stress evaluation from flume experiments using different gravel beds
Author(s) -
Petit F.
Publication year - 1994
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290190608
Subject(s) - flume , dimensionless quantity , geology , geotechnical engineering , surface finish , shear stress , shear (geology) , movement (music) , mechanics , geometry , materials science , mathematics , flow (mathematics) , physics , composite material , petrology , acoustics
Flume experiments were conducted using four different gravel beds ( D 50 + 12–39 mm) and a range of marked particles (10–65 mm). The shear stresses were evaluated from friction velocities, when initial movement of marked particles occurred. Two kinds of equations were produced: first for the threshold of initial movement, and second for generalized movement. Equations of the type 0 c + a( D i /D 50 ) b , as proposed by Andrews (1983) are applicable even if the material is relatively well sorted. However, the values of a and b are lower (respectively 0·050 and ‐0·70) for initial movement. Generalized movement requires a higher shear stress ( a + 0·068 and b + ‐0·80). D 90 of the bed material and y 0 (the bed roughness parameter) were also used as reference values in place of D 50 . They produced lower values than in natural streams, mainly owing to the fact that the material used in the flume is better sorted: clusters are less well developed and the bed roughness is lower.