Key geomechanical parameters utilized in rock engineering include Young's modulus and Poisson's ratio. Uniaxial compressive test results are essential in the evaluation of these values. This paper aims to study the process of changes of Poisson's ratio and Young modulus for intact rock during loading from micro-crack initiation to failure stage. Both Young's moduli and Poisson's ratio were calculated using the stress-strain curves. By using parametric investigation, the crack damage stress, determined for Poisson's ratio-axial stress graphs. Also, this research outline the findings that the variations among the three Young's moduli and Poisson's ratio estimated for each specimen and suggest the most effective approach for doing so. It was found, that the Poisson's rate depends on the stress value: it is linearly increasing with increasing stress till the unstable crack propagation stress. Contrary to previous ideas, our results suggest that the Poisson's ratio is not a constant for rigid rocks.
In the elastic deformation of rocks and rock masses subjected to static or dynamic loads, Poisson's ratio and Young's Modulus play an unquestionably significant role. Additionally, their impacts can be seen in a wide range of rock engineering applications, from straightforward laboratory testing on whole rocks to on-site measurements of in situ stresses or the deformability of rock masses. Rock engineering can therefore benefit from knowledge of various Poisson's ratio and Young's Modulus features. In accordance with Bieniawski (1967), the Poisson's ratio and Young's Module of rocks remains constant during linear elastic deformation but start to rise as a result of the emergence of new microcracks or the growth of preexisting ones.
The essential characteristic stress thresholds in the failure process are the crack initiation stress (σci) and the crack damage stress (σcd). While crack initiation denotes the beginning of microfracturing, crack damage denotes the beginning of crack coalescence and dilatation deformation (volumetric strain). The types of rocks, the composition of the minerals, the particle sizes, and the structural types are only a few of the variables that might affect the typical stress thresholds (Malkowski and Ostrowski, 2017).
