Geopac reached using two vibro-replacement workshops the project specifications according to the project’s schedule proposed by Quebec city.
Geopac was awarded by Québec City for soil improvement using vibro-replacement method for the future Federal building located on Estimauville site in Beauport district, Québec.
Ground Conditions and Specifications
Geotechnical investigations showed the following soil profile:
- Silty sand to Silt – very loose to dense: from 0 to -2.7
- Sand with traces to some Silt – medium to very dense: from -2.7 to – 31
- Silt and Clay to clayed Silt / very stiff to hard consistence: from -31 to -54
Ground Water Table was located at 3.5m depth from Existing Ground Level.
The following specifications had to be achieved:
- A bearing capacity of 285 kPa at ULS state at +2.65m geodesic. A total and differential settlement respectively of 25mm and 19mm under service load.
- A corrected standard penetration N1(60)cs of 23 taking into account the presence of stones columns down to geodesic elevation of -6.25m.
Ground Improvement Solutions
As a general contractor, Geopac has prepared the working platform (removal of existing foundations, removal and decontamination of a former gas tank) and has protected existing public service utilities.
Two dry method vibro-replacement workshops allowed to treat around 4600 m2 in the 48 days timeframe imposed by schedule while ensuring integrity of existing utilities.
14 standard penetration tests (SPT) and 10 pressuremeter boreholes (PMT) were performed on site. A vibration monitoring and the follow-up of induced settlement by vibro-replacement operation were also done.
Results analysis showed achievement of bearing capacity, settlement and liquefaction criterion.