Characterisation and index properties correlations for marlstone and marly limestone of Saudi Arabia

It has been a common practice to estimate the Unconfined Compressive strength (UCS) of rock through correlations that relate it to other index parameters such as the Brazilian Tensile Strength (BTS) and the Ultrasonic Pulse Velocity V_p; nonetheless, selecting the most appropriate equation to use has always been a challenge considering the heterogeneity of rocks and their variant behaviour. Therefore, the use of equations which are especially developed for certain rock type at a specific location is recommended. This paper suggests 3 equations to predict UCS from BTS, bulk density (ρ) and V_p for marlstone of the Eastern Province of Saudi Arabia. 35 core samples are collected and tested in the laboratory for UCS, BTS and V_p. Statistical analysis is performed on the experimental results, and subsequently 3 statistical models that relate BTS, V_p, and rock bulk density ρ to UCS are developed. Corrected correlation coefficients of the three models are found to be 0.575, 0.663, and 0.641, respectively. Additional reliable equation that relate the bulk density to V_p is produced with a corrected correlation coefficient of 0.95.