End restraint effects in triaxial tests on H:D = 2:1 specimens of rockfill material

Several authors have shown that end restraint effects in triaxial tests are negligible in specimens with a height-to-diameter ratio of H:D≥2. However, these works are mainly based on fine soils and sands, and few studies have focused on coarse angular soils, which typically mobilise high frictional stresses that could boost boundary effects. The aim of this study is to assess end restraint effects in triaxial tests on H:D = 2:1 specimens of rockfill material, through a comprehensive set of drained tests on loose dry samples of 150 mm in diameter. The results show that end restraint effects in coarse angular soil are not overcome in specimens having H:D = 2:1. Standard rough end platens induce higher and more scattered secant strain modulus, dilatancy and shear strength. Thus, lubrication should be systematically used in these materials.