An Investigation into the Rock Properties Influencing the Strength in Some Granitoid Rocks of KwaZulu-Natal, South Africa

• Published in: Geotechnical and geological engineering 2017-06, Vol.35 (3), p.1119-1140
• Main Authors: Fakir, M., Ferentinou, M., Misra, S.
• Format: Article
• Language: English
• Subjects: Civil Engineering; Coefficients; Compressive strength; Earth and Environmental Science; Earth Sciences; Empirical equations; Estimation; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Mathematical analysis; Mineralogy; Original Paper; Parameters; Regression analysis; Regression coefficients; Reliability; Reliability analysis; Rock; Rock properties; Rocks; Terrestrial Pollution; Tests; Waste Management/Waste Technology; Wave velocity
• ISSN: 0960-3182; 1573-1529
• DOI: 10.1007/s10706-017-0168-1

The uniaxial compressive strength (UCS) of rocks is a critical parameter required for most geotechnical projects. However, it is not always possible for direct determination of the parameter. Since determination of such a parameter in the lab is not always cost and time effective, the aim of this study is to assess and estimate the general correlation trend between the UCS and indirect tests or indexes used to estimate the value of UCS for some granitoid rocks in KwaZulu-Natal. These tests include the point load index test, Schmidt hammer rebound, P-wave velocity (V p ) and Brazilian tensile strength (σ t ). Furthermore, it aims to assess the reliability of empirical equations developed towards estimating the value of UCS and propose useful empirical equations to estimate the value of UCS for granitoid rocks. According to the current study, the variations in mineralogy, as well as the textural characteristics of granitoid rocks play an important role in influencing the strength of the rock. Simple regression analyses exhibit good results, with all regression coefficients R 2 being greater than 0.80, the highest R 2 of 0.92 being obtained from UCS versus σ t . Comparison of equations produced in the current study as well as empirical equations derived by several researchers serves as a validation. Also illustrate that the reliability of such empirical equations are dependent on the rock type as well as the type of index tests employed, where variation in rock type and index tests produces different values of UCS. These equations provide a practical tool for estimating the value of UCS, and also gives further insight into the controlling factors of the strength of the granitoid rocks, where the strength of a rock is a multidimensional parameter.