A 1950's era, six storey office tower in midtown Toronto, supported on spread footings and damaged by the action of a deep excavation on a neighbouring lot, was the subject of a major soil permeation grouting contract undertaken by Geo-Foundations in 2009. Although close to half of the grouting work was staged from outside the building using angled holes to target the soils beneath four of the undermined/ potentially jeopardized footings, the majority of the work had to take place inside the cramped quarters of the mechanical room deep in the bowels of the building's basement.
Due to the fact that the only access to the basement work was through narrow stairwells and single panel doorways, all 160 lineal metres of indoor drilling had to be performed using a portable diamond coring rig powered by an electric-over-hydraulic power pack. To further enable use of NW casing with a wireline-retrievable bi-cone drill bit, the smallest available multiple port sleeve pipe (38 mm diameter) capable of supporting permeation grout injection via double-gland packer was used, encased in a bentonite rich, low strength, cement-based casing grout prior to retraction of the NW casings out of the hole.
Maximum depth of treatment for grouting was 8 metres below surface. Permeation grout alternated between balanced cement suspension and sodium silicate solution. Cumulative totals of 40,000 kg and 47,000 kg of sodium silicate were injected at the exterior and interior of the building, respectively. All grouting work was directed in the field by Eco Grouting Specialists Ltd.
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