Driveway and road builidng is very simple, but problems happen when good enough, or close enough is used to get it done sooner then it's ready. Water is the enemy and the only thing you realy need to worry about. Dig your ditches on either side of your driveway deep enough to move the water and most of all driveway problems are solved. Where problems occur is people don't dig those ditches deep enough.
Next is making sure your road is compacted. You cannot compact dry soil, or wet soil. It has to be at the right moisture to compact. Wet soil that is pumping, or moving around is totaly useless and nothing will fix this until the soild dries out. Covering it in fabric will just keep it wet longer. Dumping rock over it will just suck up the rock until it dries out.
Most contractors will dig out the wet areas and spread it out over the road to dry, then bring in soil of the right moisture content to fill the hole and compact it. This is done for all construction projects. Just watch sometime as equipmen digs out a hole in the ground, then comes back and fills it in. It looks like they are playing games, or wasting time, but it's critical to get rid of the wet soil and build up a good base.
The thickness of rock you use seems to be dependent on where people live. Snow and freezing conditions seem to require it to be thicker. Here in the South, four inches is the minimum with 6 inches being better. The idea is to have rock that will lock together and creat a solid mass. When this happens, it will not sink into the ground, or move. It breaks apart in big chunks if you ever have to take it apart. Crushed rock with sharp angles is needed for this to happen. It also has to have varios sizes all the way down to fines so that every void is filled when compacted.
River rock or any round, smooth rock will accomplish nothing. It's pretty, but worthless for road building. I've read where large rock in the four to six inch size is put down first, then built up a certain thickness, and then topped off with 4 to six inches of road base. I can't comment on this method as it's only something I've read about. I don't understand the reasoning for this and have never seen it done in either California or Texas.
Once you have the rock in place, it will compact rather quickly by just driving over it. At first, try to drive over it along different paths just to get the rock in the middle locked to gether with the rest of it.
Going 12 feet wide sounds real nice, but it's extremely wasteful. Is there a code that requres 12 feet in your area? Ten feet is more then enough for emergancy vehicles to drive on as the law is all vehicles on the road have to be under ten feet wide. I forget the exact width in inches, but 108 jumps into my brain, but I'm not sure on that. The tires on a vehicle are usualy around 6 feet on center, give or take a few inches. With a ten foot drive, you have 2 feet of material on either side to support the weight of the vehicle. That's plenty. 12 feet wide and you have allot of material that you are paying for that you do not need. Spend the extra money on thickness and not width.
Once you have the gravel down, the biggest mistake you can make is to drag a box blade over it to smooth it out. I know this is blasphomy to many here, but breaking off the top of your rock to smooth it out only weakens the overall integrity of the rock. The rock needs to have a minimum of 4 inches to lock together. Smoothing it out quickly thins out the thickness of the rock to a point of failure. This is when you start having trouble with it and it begins to crumble, develop pot holes and even hold water.
Add rock to fill in low areas or rought spots. Never cut down yoru existing rock. Thicker is always better.
Good luck,
Eddie
