Utilization of aggregate/stone for a parking lot instead of asphalt
Utilization of aggregate/stone for a parking lot instead of asphalt
(OP)
A client of mine wants to use an aggregate(stone) in a parking area meant for empty RVs and Tractor Trailer (10 total per a day) and about 30 box trucks per day. He does not want to use asphalt pavement. The current subgrade soils are soft to medium stiff clays and silts. Does any body have a experience with using geogrid to stabilize this type of subgrade prior to placing stone(gravel)? what type/thickness of stone(gravel)should be utilized? I think he does not want to use cement or lime.





RE: Utilization of aggregate/stone for a parking lot instead of asphalt
as far as geogrids in "shallow" pavement fixes with performance criteria requirements, i'm not a fan; however, they do work sometimes (sometimes they don't). for "shallow" fixes in pavements, i usually see the contractor spend a lot of time and money fooling with stabilization geosynthetics (and hoping that it works) that could've just as easily been done with a little extra over-excavation, lime/cement, aggregate, compactive effort, etc.
my guesstimate for a real design would be (assuming the subgrade is reasonably stable): 24-36" aggregate total = 16-24"+ of #34 sized aggregate atop filter fabric and capped with 8" graded aggregate base (well compacted in thin layers-same as in pavement base course layers). if the client were mine and they wanted a more "hopeful" recommendation, i would tell them that they can make the pavement last as long or short as they want. it all boils down to $$$$. 6 inches of gab atop whatever is there might last a few years before complete failure but it also might have lots of potholes after only six months.
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
Here's where the body is burried: If you use aggregate for the "paving" surface it will readily infiltrate surface water, which in turn will allow for the traffic to disturb the compacted subgrade. Two ways to handle this: use subdrainage or thicken the aggregate to provide enough headroom to keep the dynamic loading away from the saturated surface.
We have a local RV dealer that has the same setup and they are O.K. with their gravel stagging area for RV storage.
Good luck. My gut tells me you'll need 12 to 18 inches of dense graded aggregate on a recmpacted subgrade and may not even need a geotextile.
f-d
¡papá gordo ain’t no madre flaca!
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
Pakerlax;
I've prepared gravel pavement design for clients somewhat similar to yours. A couple of things to keep in mind:
1. Look at geogrids rather than geosynthetic fabrics; they tend to provide more strength at lower strain and can reduce rutting;
2. The aggregate layer should be drained. Rain will saturate the subgrade and possibly the aggregate. The site should be sloped to drainage points prior to placing geogrid or aggregate; and
3. Maintenance; if you use a poorly graded aggregate you'll likely have surface rutting, and periodic regarding will be required. Sharp turns to access the area will result in more rutting as well.
Make sure your client's expectations for the performance of an aggregate pavement are not the same as for asphalt or concrete.
Good luck!
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
Jeff
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
Actually, many geotextiles can provide higher strength at lower strain and the geotextiles can provide separation and drainage that geogrids cannot. Stress-strain is dependant on the polymer and the way the material is manufactured. The Tensar material referenced earlier actually has low strength at low strains compared to other material on the market. For gravel roads you are often better served using a geotextile.
Check out www.mirafi.com for more info on geosynthetics. The HP geotextiles are high strength reinformcement for subgrades. You can find a local rep or engineer that can help you with their products and a gravel road design.
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
Some day there may be the need to re-grade the area. Once a grader blade catches the stuff, you won't like the result.
Also, any buried utilities now or later?. Try digging thru the stuff then. No fun.
RE: Utilization of aggregate/stone for a parking lot instead of asphalt
It is actually quite easy to excavate through geosynthetics.
RE: Utilization of aggregate/stone for a parking lot instead of asphalt