Particle Characterisation of Granular Materials and their Effect on Shear Strength

Key Researchers: Stephen Fityus, John Simmons, Klaus Thoeni

PROBLEM DESCRIPTION

Rockfill dams and waste rock dumps are enormous geotechnical structures constructed from coarse grained, granular geomaterials. Unlike most soils, which can be tested in conventional equipment at the laboratory scale, materials containing larger rock fragments defy testing without some sort of particle downsizing to fit available equipment. Despite this being a widespread and longstanding problem, little is known about the consequences of granular sample modification on measured shear strength, and there is little data to inform decisions about how scaling/scalping should be undertaken to minimise effects on measured strength. Recent research in the Centre for Geotechnical Science and Engineering suggests that the inadvertent changes in the distribution of particle shapes that occur when sample gradings are modified might be as, or more important than the changes that are imposed on the particle size. The research is seeking to understand the importance of both particle size and shape on the shear strength and behaviour of granular materials.

SCIENTIFIC AND ENGINEERING APPROACHES

• Characterisation of the potential for correlations between particle size and shape
• Systematic experimental studies of size, shape and size-shape correlations using medium and large direct shear equipment
• Systematic experimental studies of size, shape and size-shape correlations using large DEM simulation
• Assessment of the role of vertical stress, its consequences for breakage and its significance for shear strength development

APPLICATIONS

• Testing of coarse grained geomaterials for engineering purposes
• Waste rock dump design
• Rockfill dam design and performance