Experimental study of shear bands formation in a granular material

Abstract

Abstract. We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

Assessment of shear band evolution using discrete element modelling

“…Bardet and Proubet (1991) believed that the inclination angle of shear band to the minor principal stress increases with axial strain in numerical modelling of triaxial tests in plane strain condition (also known as biaxial tests) while Kuhn (1999) found the opposite. Gu et al (2014) and Jiang and Zhang (2015) reported that shear band thickness increased with axial strain, which is different from Bardet and Proubet (1991) and Nguyen et al (2017). These inconsistencies reflect the complexity of the problem, indicating formation of shear band and evolution mechanism need further investigation.…”

“…Among the current available studies, Harris et al (1995), Finno et al (1997) and Desrues and Viggiani (2004) examined the factors on shear band formation using the stereophotogrammetry technique. Nguyen et al (2017) adopted a digital image analysis tool and showed the formation of shear band involves three stages. Zheng et al (2019) applied photo-elastic technique to observe particle scale responses inside shear band.…”

“…It is noted that most of these available studies concentrated on qualitative assessment of shear band formation. Noting shear band formation is a progressive process (Nguyen et al, 2017), quantitative assessment of the evolution process is yet to be well conducted. One major reason is that it is extremely challenging to precisely identify the shear band boundaries, while an effective and accurate measurement of the inclination angle and thickness of shear band is essential.…”

“…(1997) and Desrues and Viggiani (2004) examined the factors on shear band formation using the stereophotogrammetry technique. Nguyen et al. (2017) adopted a digital image analysis tool and showed the formation of shear band involves three stages.…”

“…Noting shear band formation is a progressive process (Nguyen et al. , 2017), quantitative assessment of the evolution process is yet to be well conducted.…”