Physical-mechanical Properties of Construction Site Bedrocks of Headworks and Powerhouse of “Khobi 2 HPP” Hydrotechnical Complex

Abstract

Modern methods of rock evaluation, such as Rock Quality Index (RQD), Rock Mass Rating (RMR) and Rock Mass Classification System (Q), are used within the field of geotechnical surveys. RQD was determined by D.U. Deere in 1963, as a simple classification system of rock mass stability. While using RQD index five classes of rocks (A-E) are determined. Q value can be determined in different ways: during mapping in underground excavations, on the surface or alternatively – on basis of core description. The most accurate values are obtained during underground geological mapping. Dividing the underground excavations into several parts might be required during mapping, so that variation of Q value is moderate in each section, meaning that such variation should not exceed the rock class variation index according to the reinforcement scheme. During excavation works single blasting often represents natural section for individual mapping. A variation may take place in sections of several meters, but for showing this variation histograms can be used during mapping.