Experimental investigation of pore-fracture relationship on failure behaviour of porous rock materials

Fracturing leading to the failure of rock material is related to the inherent properties of the rock, such as pores with different peculiarities. Most of the studies focusing on the effect of porosity and pore parameters on the failure behaviour of rock materials have significant limitations in assuming the porosity as a single value representing the whole. However, due to the complex structure, the scalar quantity of porosity can differ from the actual porosity. The three-staged method was applied to determine representative porosity, and the results were verified with a CT scan on the selected samples. This study investigated the effect of porosity and pore parameters on rock materials’ failure behaviour using experimental approaches involving unconfined and confined stress conditions. It was concluded that the samples involving regular-shaped pores show stepwise failure behaviour, which affects fracturing among the samples regardless of the pore diameter prior to the ultimate failure under unconfined stress conditions. Moreover, due to samples with a wide range of porosity values, 10%, a threshold value for the porosity, has emerged, separating a different relationship with peak strength and elasticity of modulus values. The primary parameter controlling failure in samples above this threshold value is the total porosity of the sample regardless of pore geometry. In addition, up to a 15-fold increase was obtained under the confined conditions compared to the unconfined peak strength values on the samples having regular-shaped pores. This difference is only up to two times on the sample having irregularly shaped pores.