Date Posted : July 11, 2024
in : News and Events
Due to an asphalt thickness requirement of 390 mm, we had to improvise and approach the project with a unique plan to accomplish all engineering specs and technical requirements.
The methodology we came up with was the best option that this job's unique circumstance called for.
All Roads is currently undertaking the Vancouver Fraser Port Authority (VFPA) - Fraser Surrey Port Lands Transportation Improvement project, which is our second major precision milling, paving and concrete curbs and gutter construction contract at container terminal ports in recent years.
Here, due to an asphalt thickness requirement of 390 mm, we had to improvise and approach the project with a unique plan to accomplish all engineering specs and technical requirements. A 390 mm asphalt structure is quite thick when you consider that municipal roadways in British Columbia are usually paved with an asphalt thickness of 75 mm, and even highways often require no more than 150 mm.
Cargo port terminal roadways endure heaviest slow-moving traffic with a lot of start and stops, which puts more pound per square foot force on it. An engineering term to express this scenario is ESAL, which is the acronym for equivalent single axle load. That's why infrastructure construction of this type require much thicker asphalt structure.
The standard road-building practice is to put in the curb and gutter first and then do the grading and paving afterwards. However, the thickness of the asphalt in this job would pose some engineering challenges if we followed this old approach, so we had to think outside the box.
"If we put the curb and gutter in first, which is 165 mm in height, and then when we grade it down 390 mm for the asphalt, we will have over a 15" vertical drop beside the curb down to the gravel grade," explains Kyle Blakeborough, the project's superintendent.
"We determined that the curb will have no support and there is a high chance of it moving, shifting or even falling over."
To circumvent this issue, we thought to first pave two layers of asphalt: a base layer and an intermediate layer. The idea was to bring the outer edge of the initial asphalt layers to the close level as where the front pan of the curb would be. Once this was done, we proceeded to construct the curb by first putting down gravel for curb prep and then pouring the concrete using our GPS and LPS precision technologies.
Our next step was to lay down another two layers of asphalt to begin tying into the curb. At this point, the curb was only a few inches higher than the first four layers of asphalt we laid down, and therefore there was less risk to the curb's structural integrity. All that remained now was the paving of a few final layer up to our goal of 390 mm.
"In my 28 years of experience, we've never done it this way. But the methodology we came up with was the best option that this job's unique circumstance called for. And that's how we are doing it here", says Kyle Blakeborough.
"Its constructability is a little different from the road construction industry standards and that's what makes this job unique. And thankfully it worked out as planned."
All Roads Construction was contracted to address present traffic operations and to anticipate future land use changes within the project area encompassing Robson Road, Timberland Road North, Timberland Road South, and multiple intersections within the Fraser Surrey Port Lands, extending from Elevator Road to the north of Timberland Wye Crossing.
When completed, we will have done 16,830 m² of asphalt milling, 19,870 MT of asphalt paving and 1,515 m of concrete curb and gutter construction.