Correlation of UCS Rating with Schmidt Hammer Surface Hardness for Rock Mass Classification

Excerpt

The physical and mechanical properties of a rock mass need to be accurately determined when rocks are utilized as minerals or structural component. To distinguish the material properties of rock mass, engineers typically perform physical and mechanical experiments (e.g., laboratory and in situ tests) and geological observations (e.g., discontinuities, ground water). We can predict rock mass behavior, only the combination of these properties. Thus, in rock engineering, standard methods exist for rock mass classification, such as rock mass rating (RMR), Q-system and rock mass index (RMi) (Barton et al. 1974; Bieniawski 1989; Palmström 1995). The standard index can fully designate the properties of a rock mass in a complex environment and provide a reliable basis for rational use of rocks and selection of appropriate mechanical parameters (Barton 2002; Palmstrom and Stille 2007). It can also be used to develop design- and construction-related properties (Justo et al. 2010; Marinos et al. 2005; Palmström and Singh 2001). Additionally, the uniaxial compressive strength (UCS) is usually tested during rock mass classification (Aydan et al. 2014; Bieniawski 1989; China 1995; Palmström 1995). To assess rock mass quality, the average UCS is obtained because the dispersion of UCS results in laboratory testing is usually large. The average UCS indicates the strength of intact rocks in an area to some extent, and, in this process, adequate sampling and testing should be performed. This is, however, often time-consuming and costly, and furthermore it is complicated by often being unable to collect representative standard samples of some rock types. As a consequence, a rock mass cannot be immediately classified following field investigations. …