Kemptville, Ontario
2010
ECO designed and directed the pre-excavation grouting program for the excavation of a 2 metre diameter tunnel below Highway 416 near Kemptville, Ontario.
The tunnel intersected a huge pocket of loose, very pervious shot-rock. It was impossible to tunnel through this cohesionless mass that extended nearly all the way to surface.
The pre-excavation grouting program included the following:
- Designing a series of very thixotorpic, weak cement based suspension grouts to “glue” the pieces of shot-rock together, yet weak enough to allow the TBM to tunnel through the grouted matrix.
- Determining the hole layout and spacing, utilizing vertical and inclined sleeve pipes
- Injecting a weak bentonite cement based suspension grout via a serious of passes
- Real time monitoring and assessment with CAGESNS (Computer Assisted Grouting Evaluation System) to monitor the reduction in permeability.
The tunnelling subcontractor, under the direction and hands-on supervisions of ECO created an engineered, high production grouting program (more than 25m3 per day). At the end of the grouting operation, the shot-rock was properly grouted via 41 evenly spaced sleeve pipes. The average residual apparent permeability (using grout as a test fluid) was approximately 5% of the initial value. Tunnelling was accomplished without problems. No settlement whatsoever occurred and the TBM tunnelled though the grouted shot-rock without incident.