Summary

The mining industry is a major contributor to the Quebec economy. Today, mining is safer than it used to be, but it still has a higher fatality rate than any other industry in Quebec. Underground backfilling is a common practice in mining as a ground support measure to provide safer conditions for those who work underground. Yet backfilling requires the construction of barricades in access drifts near draw points to hold the fill in place. As recent events show, barricade failure is a hazard to the health and safety of all workers in mines where underground backfilling is practised.

As for all built structures, the stability of a barricade to hold fill in a stope depends on the barricade’s capacity and the load on it. Capacity varies with the materials used, the geometry (form and dimensions) of the barricade and the method of construction. The load refers essentially to the pressure exerted on the barricade by the fill. A failure with respect to any of these factors, whether in the design or building of the barricade, can represent a major hazard to the health and safety of the people working underground.

With the ultimate goal of providing the mining industry with a more reliable, more economical barricade design tool, the purpose of this research project was to learn more about the interaction between backfill and containment structures, including rock faces and barricades. Most of the project focused on theoretical and digital analyses for estimating pressure and stress in backfilled stopes and on barricades built in access drifts. That led to the development of new analytical and digital solutions for estimating pressure and stress in stopes and on barricades.

Another part of the project consisted in theoretical and digital analyses of the sizing of barricades made of waste rock. In Canada, and especially in Quebec, it has become increasingly common to use waste rock for building barricades to hold backfill in stopes. This method of construction is simple, quick and cost-effective, but there are not many options for barricade design. Between 2009 and 2012, this research team proposed an analytical solution for the sizing of waste rock barricades. The results of the project revealed the limitations of this solution. A significant improvement was achieved by incorporating more representative geometry, as well as overall and local stability within a waste rock barricade. With this improved solution for barricade design, it should be possible to size waste rock barricades more reliably and more economically.

One common practice in mines to prevent excessive pressure from fill building up against a barricade in a stope is to divide the backfilling operation into two phases: first backfill a cut and then do residual backfilling. But an unwanted interruption in the backfilling between the two phases is often necessary. This report shows that continuous backfilling of a stope is possible using geodrains in the stope and across barricades.