| This project studies the stability of the rock mass at the Niobec mine in Chicoutimi, Quebec. Since the expansion is done at depth, the stresses increase. This increase results in a higher potential for rock failure. The size of the infrastructures must be changed to take this effect into consideration. This project focused on the dimensionning of the sill pillar between mining blocks 3 and 4 using the numerical modelling software FLAC3D The pillar between the first and second block is 30m (100 feet) thick and the one between block 2 and 3 is 45m (150 feet) thick. A rock mass characterization of the site has been made prior to numerical modelling. The characterization consisted of structural geological mapping on levels 1150 and 1450, laboratory testing of rock samples and insitu stress measurements. Geological mapping was compared to two other studies made on levels 300 to 1000. Two major sets were identified with a third one becoming more important at depth. The laboratory testing included uniaxial compressive tests, diametrical compressive tests and triaxial compressive tests. The uniaxial compressive strength of the rock substance was found to be 128 MPa and the tensile strength, 8 MPa. Laboratory testing results were used with the Roclab software to establish Hoek-Brown and Mohr-Coulomb failure criterion parameters at the rock mass scale. The stopes were then modelled and the parameters obtained from the characterization entered in FLAC3D Results were compared with those from Examine 3D software to validate simplifying assumptions made with the FLAC 3D model. Following this verification, various options were analyzed. It was first observed that the use of backfill had little influence on the stability of the rock mass. (Abstract shortened by UMI.)... |
