RQD PREDICTIONS BASED ON DRILL PERFORMANCE PARAMETERS

In tunnelling and in other underground constructions, a detailed knowl edge of the rock mass to be excavated is essential for reasons of safe ty, reinforcement need and cost and time schedule for the excavation. This paper presents a new approach to how drill performance parameters can be used for Rock Quality Designation (RQD) prediction. Prediction s are based not only on traditional parameters as penetration rate and torque, but also on the variability of each parameter which shows a c lose correlation, to fracturing. Since predictions are based on drill monitoring data with high resolution, the prediction can provide detai led information of the structural geometry of the rock mass ahead of t he operation. Examples are given from a railway tunnel in northern Swe den, built in granitic bed-rock.