Gravel road building: anyone here know anything about it?
 

I need to improve some of the roads at BHF and would like to hear any input/experiences that folks have had doing this sort of stuff.

Randy, my dad was in the road-building business. All I can tell you is to be sure you get any clay out of the roadway before you start putting down gravel. Clay is like a sponge when it gets wet and if you're driving heavy machinery, trainlers, etc. over it the gravel will just disappear into the clay when its wet.

Good luck.

Proof roll the sungrade before placing any fill with at least a loaded 10 wheel truck. Look for areas where the grounds pumps. If you are unfamiliar with the term "pumping", think of what happens on a water bed when you apply a load in one place. The surface of the bed around the load rises up, and the area where the load was placed, lowers. As the load moves across the surface of the bed the surface seems to roll. Thats pumping. In soil, it is caused by the load being carried on the water in the soil, as opposed to the solid soil paricles themselves.
If it "pumps" when you proof roll, you have a few options:
1) Cut out and remove the wet soil. This will not work if you have a high water table as any new soil will quickly become saturated, and pump. What do you get if you add a ton of stone to a ton of mud? ( ans--2 tons of mud)
2) Cut out a few extra inches of soil and place either a geo-grid, or a geo-cloth (woven). The material holds the stone fill together so it acts like a mat and the load is distributed better.
3) Do nothing and wait for the road to deteriorate.

Contact a local geotechnical engineer for specific advice. If you are in the Mid Atlantic, call me ( 410) 808 1422
Michael

Michael,
Thanks for the pointers. Based on your description, I think we definitely have a couple of locations that will cause problems because of water in the soil.

The road in question is a new installation through a pasture to the barn. I know that the site has about 10" to 24" of packed, silty sand on a clay pan that is of unknown depth. Until now, the ad-hoc road we use saw little traffic and what was there rarely weighed more than 5000-7000 lbs. Now, it has the possibility of needing to support Dad's 30+ ft motor coach (25,000+ lbs) in all conditions.

Since the first, we've had 6"+ of rain and lately, traversing the road in a car or pickup is dicey at best. It will be interesting to see what happens later this week when they leave in the coach.

Am I correct in assuming that in questionable locations, you would prep the roadway (ditch, contour, crown) then apply the geomat/geogrid material before spreading gravel?

Our house has had a gravel driveway for on 100 years,had to redo it 15 years ago,150'long.

First all the old gravel and substrate was bucket loaded away,then the hard packed soil was regraded with a slight "crown"in the middle to facilitate drainage.

Next crushed concrete was spread out and pounded in with a final layer of 1/2-3/4 riverstone,nice,round tan pebbles in use since colonial times.

That sounds somewhat like I need to do with the existing roads. They are already ditched and crowned but have suffered from never getting a gravel layer. Since they're already packed pretty well, I'll probably scrape a little and recrown then come back with a couple of inches of pit run gravel. The big difference is that this one is a shade over 3100' from the gate to the cabin.

Funny.
I just box bladed 13 yards of 'flex base' on my new drive. Looks like crushed concrete to me...
Good base stuff.

Improve a gravel road?
 

Asphalt paving. :D

Grade the subgrade ( that sounds confusing doesn't it) then fix the bad spots and place and compact the gravel.
I don't like round stones as they can tend to act like ball bearings and roll over each other. I prefer crushed gravel at the particles will lock together.

Heck, just do it the Ky way. Put down a huge amount of gravel and run coal trucks over it for a long time. More gravel, continue trucks. By the time the mine is played out, you have a nice solid base for a real road. Only probelms are that you A: need a coal mine and B: mine may be productive for LONG time. Still, you be amazed how much compacting you get out of a grossly overweight coal truck.

I suppose “roadbase” varies to the local. Around here it's a combo of crushed rock, sand, dirt and sometimes a little lime is added. Spreading about 3-4 inches down the crown will be near a 100 ton for 3000' and it runs $9.50 here. That makes a fine drive by itself, but topping with a crushed rock will look better and double the cost. It's almost like painting in that the base will mirror the surface it's put over. The crushed rock then will kind of seek out the bad spots as it's driven on so the combo of the two works best.
You don't get that much traffic on a driveway but it's sort of a point of pride to do it right.

When I did the road at the ranch I had one spot that was soft. I kept throwing chunks of concrete, rocks, bricks... in until they made their way to China. Eventually the spot firmed up.
BTW, Best price I found for base material (crushed concrete) was $285/10yards delivered.
Although, I am finding all sorts of wire and rebar pieces in it.

At one time I got what they call "wash-out" cheap. Waste material washed out of the cement trucks. Packed very nice.

I've checked into getting washout around here and, while the price is right, it's a hit-or-miss proposition to actually acquire the stuff. Washout supplies vary greatly since there isn't a huge amount of construction taking place in the area. A rough calculation shows I'll need about 120 yds for an 8' wide road with 2" of gravel.

Cartage is an issue too since the nearest ready-mix outfit is about 9 miles off and the next closest two are about 14 miles.

I am in the process of doing the same thing except I have NYC curb at the edges of my driveway. They are solid Granite 5" wide x 12" deep x 84" to 110" long. I set the curb on Bluestone screenings then put in the RCA. I think I will go with 5/8" riverstone because it has the old fashioned look but is large enough to not stick in shoe or tire treads. My driveway is 275'. I priced out Belgian Block compared to the solid curb and it was cheaper for the solid curb because I bought a full load from Georgia. It is a traditional looking driveway that will last several lifetimes. If the frost ever heaves the curb, it can be reset.

If frost ever heaves my curb I'm moving further south. ;)