Observing strain localisation processes in bio-cemented sand using x-ray imaging

Francesco Tagliaferri (1, 2) , Jack Waller (3) , Edward Andò (1, 2) , Stephen A. Hall (1, 2) , Gioacchino Cinno Viggiani (1, 2) , Pierre Bésuelle (1, 2) , Jason T. Dejong (3)

1 3SR - Laboratoire sols, solides, structures - risques [Grenoble]
2 GéoMécanique
3 CEE - UC Davis - Department of Civil and Environmental Engineering [Univ California Davis]

In-situ x-ray tomography has been used to follow deformation processes in 3D during two triaxial compression tests, one on a specimen of bio-cemented Ottawa 50-70 sand and the other on a specimen of the non-cemented sand. The global stress-strain responses show that the bio-cementation process increases the shear strength (peak deviator stress is approximately doubled), and causes the material to exhibit a linear behaviour up until peak, as well as increasing the dila-tancy angle. The residual strength of the two samples is very close at large strain. Quantitative 3D digital image analysis (porosity, cement-density and strain field measurements), reveals that a dilatant shear band gradually develops pre-peak in the reference material. The cemented sample however undergoes an abrupt change of deformation mechanism at peak stress: from homogeneous deformation to localised dilatant shearing, which is associated with a local loss of cementation.

Mots clés: Bio-cemented sand; Strain localisation; In-situ x-ray tomography; 3D-DIC

Domaines: Mécanique des solides [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Science des matériaux [cond-mat.mtrl-sci]; Ingénierie de l'environnement; Matériaux

Francesco Tagliaferri, Jack Waller, Edward Andò, Stephen A. Hall, Gioacchino Cinno Viggiani, et al.. Observing strain localisation processes in bio-cemented sand using x-ray imaging. Granular Matter, 2011, 13 (3), pp.247 - 250. ⟨10.1007/s10035-011-0257-4⟩. ⟨hal-01570995⟩