Effects of model scale and particle size on micro-mechanical properties and failure processes of rocks—A particle mechanics approach

A numerical procedure to determine the equivalent micro-mechanical properties of intact rocks is presented using a stochastic representative elementary volume (REV) concept and a particle mechanics approach. More than 200 models were generated in square regions with side lengths varying from 1 to 10 cm, using the Monte Carlo simulation technique. Generated particle models were then used for the calculation of equivalent micro-mechanical properties. Results with a core sample of diorite from Äspö, Sweden, show that the variance of the calculated values of mechanical properties decrease significantly as the side lengths of particle models increase, reaching a REV side length about 5 cm with an acceptable variation of 5%, which is equal to the minimum diameter of rock specimen for uniaxial compressive tests suggested by ISRM. The complete stress–strain curve of the diorite rock sample was predicted under uniaxial compression, as the basis for evaluating the damage and failure processes. The unique contribution of this paper is its study on impacts of sample size and particle size distributions on mechanical behaviour of rocks when particle mechanics approaches are used.