Discrete element analysis of the effect of pore size and pore distribution on the mechanical behavior of rock

The effect of porosity, pore size and pore distribution on rock deformational and strength characteristics is studied in this paper, using a bonded particle model. Several uniaxial compressive and tensile strength tests were conducted on the numerical specimens with different sizes. Different pore distributions and pore sizes were used. It is shown that in addition to porosity, the pore size can have drastic effects on the elastic modulus, crack initiation stress and rock strength. The ratio of uniaxial compressive to uniaxial tensile strength of the simulated material is affected by the pore size as well. The simulated material shows statistical size effect in tension and crack initiation stress, but this phenomenon is not ideally captured in compression. The size effect in tensile tests was attempted to be modeled by Weibull distribution with relative success. It is shown that the size of representative elemental volume depends on the rock property which is being investigated. For example, the size of representative elemental volume for rock elastic modulus is much smaller than that for the crack initiation stress. It appears that the size of representative elemental volume is a function of macro-pore size.