Physical and Numerical Modeling Study of Jointed Rock Block Strength Under Uniaxial Loading

: To simulate soft rocks, (a) a mixture of plaster of Paris, sand and water was used as a model material. Thin galvanized sheets were used to create joints in blocks made out of the model material. To investigate the failure modes and strength, jointed model material blocks of size 30 x 12.5 x 8.6cm having different joint geometry configurations were subjected to uniaxial compressive loading. Results indicated three failure modes: (a) tensile failure through intact material, (b) a combined shear and tensile failure through joints, and (c) a mixed failure of the above two modes depending on the joint geometry. The fracture tensor of a jointed mass has the capability of integrating the effects of number of fracture sets, fracture density, and distributions for size and orientation of these fracture sets. The fracture tensor component in a certain direction provides the directional effect of the fracture tensor. Results obtained from the experiments were used to develop a strong non-linear relation between the fracture tensor component and the jointed model mass strength. Some of the laboratory experiments conducted on jointed model material blocks were simulated numerically using the distinct element method. Obtaining good agreements between the experimental and numerical results through the distinct element method was found to be not a trivial exercise. However, with careful selection of suitable material constitutive models for intact material and model joints and accurate estimation of parameters of the constitutive models through laboratory testing, it seems possible to obtain good agreements between the experimental and distinct element numerical results.