Vertical Wick Drain Supply & Install

LOCATION: CFB- Esquimalt Victoria International Airport, Victoria, BC

TIMEFRAME: November 2011- January 2012 SCOPE OF WORK: Supply/ Install - Vertical Wick Drain

PROJECT PARTNERS Owner: Dept National Defense Design Consultant: Stantec Contractor: Knappett Projects

Challenge

DND is in the process of constructing a new helicopter squadron base in time for the arrival of a new fleet of CH-148 Cyclone helicopters in 2013. The proposed area to build the new base and tarmac was a former refuse site during WW2. Soil conditions where the new tarmac is going to be built were variable; ranging from very soft to very hard. In order to accommodate landing a fully loaded C-17 transport airplane (600,000 lbs), the tarmac can handle only the slightest bit of settlement. In order to achieve minimal settlement the ground below the tarmac had to be improved. Traditional methods use soil preloading for a determined period of time to ensure the sub surface soil becomes consolidated. Unfortunately, due to the tight time frame to construct this base they needed a solution to speed this process up. Another challenge that presented itself was to work alongside the current commercial airplane runway at the Victoria International Airport without disrupting flight schedules. Height restrictions for equipment working near the runway also became a challenge due to safety concerns of the air traffic control tower at the airport.

Solution

In order to speed up soil consolidation times the design engineer decided to employ the use of vertical wick drains prior to placing the preload soil. Layfield mobilized its wick drain equipment and crew to site to supply and install approximately 125,000 lineal meters of wick drain, which equated to 40 ten hour work days. The wick drain was installed to a 10 meter depth and spaced every 1.5 meters in a triangular pattern to ensure the level of consolidation required was met. The Layfield crew also adjusted work hours to accommodate the airport schedule and safety concerns, and were able to install the wick drains bordering the current airport runway during off hours.

Results

Thanks to the efforts and flexibility of the Layfield Project Team, the wick drain installation was completed on time and on budget. Even though every weather element was encountered; including snow and high winds, the Layfield crew pushed on and met the tight deadline. The end result was that the contractor was able to put the preload on site quicker, which in turn will allow them to construct both the new helicopter squadron base and tarmac on schedule. In addition there was not one disruption to the airport schedule as wick drain installation alongside the airport runway was done between the hours of 12:00am – 5:00am to ensure there was no interference. Both the owner and contractor were extremely impressed with the service level and professionalism provided by Layfield.

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