Remote monitoring of underground excavations by means of deformation measurements (CIUS)

Abstract

The Niobec mine is located in St-Honore 15 km north-east of Chicoutimi (Quebec, Canada) and produces Niobium at a rate of 815,000 metric tones annually. Exploitation is done using the Long Hole method with sill and crown pillars at the levels 300-600 (90-180m) and 700-1000 (200-300m). For economic reasons, no backfill has been used at this mine. As a result, stopes with a minimum 100 meters in height have been left open since excavation. Mining activity take places in a carbonatite pluton located in the Pre-Cambrian Shield. The carbonatite and host rocks are capped by flat lying limestone. Six CIUS (Cylindre Instrumente de l'Universite de Sherbrooke) have been installed at this mine. The CIUS is a cylindrical concrete inclusion, instrumented with vibrating wires, installed in a borehole and used to follow the variations of stress and deformation in the host medium (rock mass). The objectives of instrumentation at this mine by the CIUS are to monitor the variations of stress and deformation. The thesis presents the development and application of a probabilistic model for prevention and prediction of in-situ rock mass failure. The programming procedure of a rock failure warning system (Alarm System) using the CIUS' data has also been presented. The algorithm of this model operates on the basis of the detection of the anomalies on the deformation rates, recorded by the CIUS. The warning system contains the CIUS and an acquisition system, developed at the Universite de Sherbrooke (CAIUS), in which the algorithm of the preventive model can be implanted. It has been shown that this unit can offer the continuous remote monitoring of underground structures, regardless where they are located.