Effect of compression and tensile stresses on elasticity modulus and poisson's ratio of rock material

Modulus of elasticity (E) and Poisson's ratio (V) are the two most important elastic parameters of rock material that are frequently used in geotechnical designs. The reliability of these parameter values is only possible if they are determined in accordance with the standards. Unreliable values and wrong uses affect both the cost and reliability of the design. One of the worst uses is the use of compression modulus of elasticity (Ec) and Poisson's ratio (Vc) as they can be determined more easily instead of the tensile modulus of elasticity (Et) and Poisson's ratio (Vt). However, studies show that there are important differences between these parameters. In this study, the relationships between Ec and Vc parameters and Et and Vt parameters of medium and low strength rock material were investigated. For this purpose, core samples were collected from 4 different lithologies, and uniaxial compression and direct tensile tests were performed on these samples. During these experiments, the axial and lateral deformations in the samples were measured and the Ec, Vc, Et and Vt values of the samples were determined using the obtained deformation values. In the last stage, the obtained values from experiments studies were evaluated statistically, simple and multiple regression analyzes were performed to determine the relationships between these parameters. According to the statistical evaluations, it was determined that the Ec value of the rock material was 36% higher than the Et value, and the Vc value was 27% higher than the Vt value. According to the regression analysis; Multiple regression analyzes using the rock material Ec, Vc and uniaxial compressive strength as independent variables have the biggest correlation coefficient (R). As a result of this study, empirical equations were suggested to predict the Et and Vt values of the medium and weak strength rock materials. Keywords: Modulus of elasticity, Poisson's ratio, Compressive stress, Tensile stress, Rock material