Trenching using GeoBreak Expanding Grout to remove granite rock on Douglas Street where blasting was prohibited – Victoria, BC – Complete January 2019.
Scope of the Project
- Underground utility installation
- Hydraulic hammer proved to be inefficient on tough rock
- Non-explosive demolition technique required (Expanding Grout)
- No available free face
Throughout various areas of downtown Victoria there are aging city infrastructure and heritage buildings where a shock wave produced from commercial explosives to break rock can pose a concern. For this particular area on Douglas Street, no blasting by any means was allowed. The contractor originally attempted to break the granite mechanically by hoe-ramming. The topography allowed for a machine to create more dust than fragmented material. A drilling contractor was used to drill 1.5” hole size with 12” spacing for the trench line using a small drill rig. GeoBreak’s Expanding Grout was poured and tarped off during the expansive cycle through its weekend use.
Which GeoBreak Products Were Recommended
GeoBreak Expanding Grout Type III was recommended for this rock breaking project based on ambient/topographic conditions.
The expected outcome of using GeoBreak Expanding Grout was to break the rock in the trench to allow for a machine to excavate the broken material.
GeoBreak Expanding Grout broke the granite where the bucket’s teeth could pull and excavate the loose material. 5 of the 6 feet in depth was excavated out with a machine. The remaining foot was cracked which provided aid for the use of the hammer. Delayed pouring was used similar to sequential firing related to blasting. The perimeter holes and 3 feet on where the free face would be created were poured first followed by the remaining middle holes 6 hours after. The delay pouring allows for the perimeter and front face to break first to allow for the middle holes in the trench to become more efficient during their breaking cycle.
Final Thoughts From The Project Contractors
Hoe-ramming the rock was taking too much time given how hard the rock was and the depths that were being broken. Without blasting this was the first approach that was taken. GeoBreak provided their support with product knowledge, recommended drill patterns and delivery on site as well as a site visit to have a look at the rock and our current situation. A drilling contractor was used to drill the holes for the trench. The compound is mixed with water and then poured into the drilled holes. Holes were drilled mid-week and poured later in the week. The rock was broken and excavated on the Monday following the weekend. The Expanding Grout works providing a non-explosive, quiet, vibration free alternative when a hydraulic breaker is no longer effective and when you are hammering larger rock cuts.