Q-factor by spectral ratio technique for strata evaluations

Abstract

The laboratory estimated quality factor ‘ Q’, a function of acoustic wave speed ( V), amplitude ( A) and frequency ( f), were chosen for in situ strata evaluation of rocks of the right bank canal of upper Wardha, Maharashtra, India, using the spectral ratio technique. Eleven core samples of compact, amygdaloidal, and vesicular basalts, were characterized by their Q values. The Q-factor determined using the spectral ratio technique with centre frequency of 500 kHz, is found to result in differing values for compact, amygdaloidal, and vesicular basalts over ranges 10–14, 4–6, and 2–4, respectively. The specimens belonging to amygdaloidal and vesicular basalts with secondary minerals and calcareous intrusions in the vesicles have a very low Q value and a very low yield of rock mass that is not proportionate to the energy generally used in blasting operations. A correlation of Q=0.26RQD(%)+3.68 between the laboratory-measured Q value and in situ rock quality designation (RQD) (data obtained from the recovery of the exploratory borehole core samples) provides a useful means of understanding geological strata in rock mass recovery evaluation. The lower Q values implied higher energy requirements for effective excavation of the rock masses.