Assessment of mechanical behaviour of rockfill materials using triaxial and direct shear tests

The mechanical behaviour of rockfill materials and aggregates depends, not just on particle size and compaction, but mainly on their strength and lithological properties. In this research two types of large triaxial and direct shear tests are performed on rockfill materials. This Paper compares the stress-strain laboratories tests; behaviour of sandstone and andesibasalt materials in triaxial compression tests (300 x 600 mm) and direct shear tests (300 x 300 mm). The study evaluates two kinds of aggregates showing different lithological properties and the result revealed that how the same particle sizes aggregates behave differently due to different lithology and test procedures. The results in this research show that shear strength of hard and strong rockfill mass (andesibasalt) is more, and the deformability is less, compared to weaker rockfill materials (sandstone), and this variation increases with increasing confining stress and surcharge.