The Grand Condominium, Phase II, Cambridge, Ontario
Soil reinforcement achieved using Geopier Ground Improvement® Systems has become commonplace in North America, and most certainly in Ontario since their introduction in 2006. Soil Reinforcement systems—such as replacement and displacement Rammed Aggregate Pier® Systems—have been installed successfully on countless projects throughout Ontario.
New and exciting soil reinforcement technologies are now allowing owners, developers and contractors to realize significant cost and schedule savings in increasingly poor soil conditions.
The Grand, Phase II is a 12-storey condominium structure with two levels of below grade parking situated on the east bank of the Grand River in Cambridge, Ontario. A similar condominium (Phase I) was constructed previously just north of the Phase II location. The developer’s goal was to create a centrally-located development that would provide its occupants with incredible views of the water and historic Galt’s downtown skyline.
Building on the bank of a river comes with its own unique challenges which the project team needed to overcome to get this development out of the ground. During the project planning phase, it was discovered that the soil conditions at this site would not be suitable for the use of spread footings, which is typically the most cost-effective solution when the soils are of good strength.
These soils generally consisted of 2 to 5.5 metres (7 to 18 ft.) of very loose to compact sandy silt (ML) fill underlain by very loose to loose sandy silt to silt (ML) soils with trace to frequent organics to a depth of 6 to 8 metres (20 to 27 ft.). The fill/organic silt was found to be underlain by a compact to very dense sand and gravel deposit. The ground water level at the project site was generally consistent with the level of the adjacent river at a depth of about 5 to 7 metres (7 to 22 ft.) below the existing grade.
The team required a cost-effective foundation solution that could be installed with minimal delays to the project schedule. Based on the highly compressible nature of the soil profile, the geotechnical engineer recommended that the structure be founded on a deep foundation system; however, installation difficulties, cost overruns, and schedule delays during installation of a helical pile solution on Phase I of The Grand development created concern for the project schedule for Phase II.
Ultimately, through discussions with GeoSolv, the Geopier GeoConcrete® Column system was selected for its cost-effectiveness, speed of installation, and ability to provide for high capacity standard footing construction. The foundations of this structure were subject to column loads of up to 6,675 kN (1500 kips), wall loads of up to 100 kN/m (7 kips/ft), and mat pressures of up to 380 kPa (8ksf). The Geopier GeoConcrete System (GCC) was designed to limit total settlements to less than 1 inch and differential settlements to less than ¾ inches. The improved bearing capacity provided for standard spread footings by the GeoConcrete System was 450 kPa (9.4 ksf) at Serviceability Limit States (SLS) and 650 kPa (13.6 ksf) at Ultimate Limit States (ULS).
Installation of the Geopier elements was conducted rapidly within the basement excavation with one crew averaging 40-60 GeoConcrete elements per day. Full-time quality control was provided by GeoSolv’s experienced construction team and the GCC capacities were verified in the field by a full-scale load test which demonstrated less than 4.5 mm (0.18 in.) of deflection at the maximum design load.
Construction of The Grand Condominium Phase II was completed in 2015 and stands as an important structure in Cambridge’s growth plans.
Additional information on the Geopier GeoConcrete System can be found here: https://geosolv.ca/rigid-inclusions/geoconcrete/