Abstract
Multi scale projects of civil, mining, and oil and gas drilling require to determine rock strength as main property of surface and subsurface rocks for safe structures, economic mining operations, as well as drilling performance optimizations. The Unconfined Compressive Strength (UCS) as a main rock strength test is considered a time consuming for sample preparation, costly, and unaffordable. However, it is required for correlations for rock strength obtained from other tests. A semi-Point Load Strength Index (Semi-PLSI) is proposed in this research as a new approach to estimate rock strength. The objectives of this research include reducing testing costs, simplifying sample preparation and testing procedure, precisely localizing, stabilizing, and balancing specimens while testing, and improving accuracy and repeatability. For this test, various sample dimensions and length to diameter ratios are prepared from granite rock type. A 400 (kn) Geomechanics Frame is used for testing and an advanced data acquisition system is utilized for data recording. Data obtained from Semi-PLSI are correlated with data obtained from two main strength types including UCS that represent the shear fracture strength and indirect tensile strength (IT) that represent the tensile fracture strength. Data correlation also includes measurements of ultrasound primary and secondary wave velocities that represents nondestructive data measurements. The good correlation agreements and the verity ways of estimating the strength enrich this new approach of the Semi-PLSI proposed for UCS estimation and pave the road of more research.
