Road construction on old landfill

[dellbs]

I'm in the process of designing a road part of which will be constructed over an old landfill. The landfill hasn't been used for 20+ years, there is about 16" of soil over the "fill" and the fill is about 10 feet deep.

This is not a road which will get constant traffic, it will serve as access to a boat launch area so loadings will be fairly "light" only the occasional service trucks.

Any suggestions, anyone done this before? If so, generally how was settlement accounted for? Utility trenching? This may seem like a geotechnical question, but I'm guess I'm looking for case study type responses.

 

[pigdog]

Hey dellbs,
We found a similar site at a road-widening project for I-85. The engineers decided on "dynamic compaction". A crane comes and drops a big weight and stomps the ground down.

On your site, the easiest alternative is to treat it as a maintenance issue and repair the road as it settles. A gravel surface would probably be easiest to maintain. 20 years ago brings it into the time of plastic trash bags, acting like hermetically sealed baloons, so you cannot assume that settlement has already occurred. With an increased load, it will probably start to move.

Good luck,
pigdog

 

[dellbs]

Thanks.

 

[Jim6758]

Building a road on an old landfill can be a maintenance nightmare. Some options you might want to consider are:

1. Use of geogrid under a rock sub-base.
2. Compaction grouting combined with deep dynamic compaction.
3. Use of "grout piles", sometimes called Vibro piles.

Of the three above, the geogrid is likely to be the most economical.

 

[jheidt2543]

On a project over a marsh area in Wisconsin, the State DOT paved the section with asphalt over an extra thick stone base, knowing it would settle. They then monitored the approximately 1/4 mile strech. As the pavement settled, they would add another layer of asphalt. Over the years the settlement stopped, so they put concrete pavement over the asphalt. When they cored the the asphalt they found it almost 3'deep! Just another way to "skin the cat". However, that was before all the geotextile fabrics we now have. Using them is quicker and better.

 

[Grader]

Keep in mind the value obtained for the money you spend on a project. This is a job that you could dump a pile of cash and not receive the expected result. I can assure you that short of removing the old dumpsite in the area of your roadway, the road will eventually move. I believe pigdog has the best solution. Grade it, rock it and then maintain it as needed.

 

[KRSServices]

Your best bet is to calculate your structure using a soaked CBR value of 3. if the "fill" is landfill refuse, I would suggest designing an alternate alignment if possible because the cost to design, construct and maintain will be quite substantial versus an alignment over undisturbed or native soils. The cost for additional reinforcement alone would be worth procuring land for an alternate alignment, notwithstanding the fact that I do not know all the circumstances.