The impact of stress history on bed structure

Auteur(s) et Affiliation(s)



Description :
Recent research has started to focus on how prolonged periods of sub-threshold flows may be capable of imparting structural changes that contribute to increased bed stability. To date, this effect (termed stress history) has been found to be significant in acting to increase a bed's critical shear stress at entrainment threshold. This paper uses high resolution laser scanning to quantitatively ascertain the granular mechanics underpinning the relationship between stress history and entrainment threshold for beds of a range of grain size distributions. Two laser displacement scans of the bed surface were taken, one prior to the antecedent period and one after this period, so that changes to surface topography could be quantified. Rearrangement of bed surface structure is described using statistical analysis and two-dimensional (2D) semi-variograms to analyse scaling behaviour. Results reveal vertical settlement, changes to bed roughness and particle repositioning. However, the bed grain size distribution influences the relative importance of each mechanism in determining stress history induced bed stability; this is the focus of discussion in this paper.


Type de document :
Article de périodique

Source :
Earth surface processes and landforms, issn : 0197-9337, 2013, vol. 38, n°. 7, p. 717-727, nombre de pages : 11, Références bibliographiques : 1 p.

Date :
2013

Editeur :
Pays édition : Royaume-Uni, Chichester, Wiley