Study of Material Failure and Strength Degradation in Argillaceous Packsand Samples

The compressive strength and failure evolution of argillaceous packsand samples were measured via uniaxial and triaxial compression tests under varying confining pressures.An XJ-1 portable shear apparatus was used to obtain shear-compressive stress curves of rock blocks.These are a measure of the material strength of the rock.The degradation in strength of the rock after failure was studied by comparison to the Mohr circle obtained from compression experiments.The influences of different experimental methods,of damage extent,of the effect of size and of material anisotropy on the degradation in rock strength are discussed.The results show that hoop and volumetric strains increase linearly after the peak-load point in the failure process and that the material strength of the rock drops as the failure process develops.It is also shown that the rock shear strength displays a size effect.