Drill Soil Nails permit long-term Slope Stabilization

Context

The project is a new hydroelectric facility under construction on the Sainte-Anne du Nord River in the community of Saint-Joachim, Quebec, in southeastern Canada.

The run-of-river facility is being built next to the 60m high Sainte-Anne Waterfalls and will have a nominal capacity of 23.2MW after its completion, scheduled for November 2016. The facility will produce an average of 82,400MWh of renewable energy per year, which is equivalent to the needs of 4,800 local households.

The project involved extensive slope stabilization to ensure a reliable access to the powerhouse site. Due to challenging access constraints and the need to prevent any visual impact on the popular tourist attraction of Sainte-Anne Falls, the decision was made to construct three permanent retaining walls.

The main retaining wall crosses the Cap Tourmente fault line, where challenging ground conditions were anticipated and effectively encountered. These included very steep natural terrain slopes, extremely dense soil in the lower sections of the wall and the presence of large boulders.

Solution

For the retaining walls, DYWIDAG supplied a total of 1,671 permanent Dywi Drill Hollow Bar Anchors that were used as soil nails. The highest sections of the soil nail walls are 20m high and had to be stabilized by up to 11 rows of up to 18m long soil nails. The Dywi Drill Hollow Bar Systems were supplied with carbide drill bits in diameters of R32N, R32S, R38N, R51L, T40 and R51N.

All hardware was galvanized for long-term corrosion resistance. Following soil nail installation, a permanent concrete facing was applied on top of the shotcrete retaining walls to guarantee a minimum service life of 75 years.