Private access road repair. 3

[msquared48]

Got a problem with a gravel access road. It is only about 1000 feet long, but depends into and out of a small gulley to serve three residences. The slope is up to 10 percent. The road has had the problem with washboard in and tuts. As a result, one of the owners put 2 to 3 inches of 3/4" minus over the top and tried to compact it. Now it is worse than ever, and I had to call a towtruck to be pulled out last night.

My question is, without totally redoing the road, can the addition of 1.5" minus compacted stabilize the 3/4" layers so that you can get sufficient traction to climb the grade without spinning wheels?

Fyi, the alignment is of a poor design with a sharp curve at to one side of the gulley, making adequate momentum difficult to msintain.

Mike McCann, PE, SE (WA)

 

[oldestguy]

I have been thorough this type of thing. The erosion due to rain on semi rutted areas as well as fast driving vehicles (causing wash board) had to be dealt with. If possible change the upper few inches to a well graded mix with a small amount of silt-clay (Passing 200 sieve). If possible add a few percentage of rock salt. The salt will keep moisture present. The moisture is necessary for slight binding. Periodic grading needed to remove ruts and wash board, followed by each driver taking a different track, not the same ruts. Preparation requires considerable blading back and forth of these materials to get a thorough mix. Adding of a dense, well graded highway spec base course might be easier, but getting the salt in requires blading. Shape up things so drainage goes off to the side, not down the roadway. Other forms of stabilizing may be tried, but salt along with the fines in a well graded mix can't be beat.

On some slopes, without side ditch drainage you may need a few diagonal cut and hump to divert surface water now and then. Hard to maintain, but may be needed.

Finally, if all fails, a local contractor may do a double chip seal, but life is unlikely more than 10 years. 3 or more inches of blacktop was my final cure. 2 inches is not sufficient.

 

[oldestguy]

One added point. In addition to slower speeds, on steeper slopes 4 wheel drive engagement will help a lot for up-hill traffic to minimize wash boarding. It's tough to get speeders to cooperate, I know.

 

[Ron]

Mike...consider tilling in 3 to 4% (by weight) portland cement with the 1-1/2" aggregate you mentioned. Will prevent washouts and still have sufficient roughness to allow traction. Contrary to convention, don't compact to smooth surface but compact enough for cohesion with the cement. This will allow rough texture.

 

[msquared48]

Ron:

I have, but was unsure of the amount to use. Problem is the 4 to 6" of 3/4" minus there now causing the slipping problem. Might have to remove some of that prior to installing the mix you recommend, saving that to fill in ruts later. Unfortunately, it is all about the money...

Thanks Ron.

Mike McCann, PE, SE (WA)

 

[ACtrafficengr]

Wouldn't it be a good idea to test a few samples before designing a repair? Especially if you're thinking of paving it. A good gravel road makea a lousy base for a paved road. Then again, this isn't a good gravel road...

 

[cvg]

unfortunately, a lot of speculation without much data. other than the slope, which is not particularly steep and the alignment, which may be a significant issue, what is causing the problem? is it drainage causing washout? is it drainage causing wet/soft subgrade? are there grader ditches? is the subgrade clay? is this a creek crossing? was the original gravel open graded or rounded or well graded crush? is the road crowned or inverted? is rutting the main problem or washboard? does it ever get graded? how much traffic and what kind? any buses or trucks?

 

[oldestguy]

The go slow approach is best. Depending on frost potential, any one of the stabilization treatments can be destroyed. I know that salt has worked well in New York state. The only place I have seen cement stabilization work in northern climates is in improving a muddy subgrade, later covered up with base course, etc.. Thus, a trial section or two for any stabilization is the way to go before going whole hog.

I have presumed there is a decent sized tractor (30 hp and up) with rear blade available for periodic maintenance in any case. A rear PTO tiller would be a great asset for the stabilization work.

 

[dhengr]

Mike:
It sounds like the 3/4" minus gravel lift just laid down several inches of marbles to drive on; no compaction or binder, no traction, in fact, unraveling under any wheel traction force. Well graded crushed gravel compacts and locks together much better, and should contain some small percentage of clay for binder. I agree with Oldestguy, I’ve had good luck with his general method on a mile long driveway, where it has had soft spots, etc. It’s all local materials, more reasonable price and work effort to start to make it work, or to rework some areas to improve them. At the moment bulk cement seems kinda hard to come by, at least in MN and WI, and is just not easily available to the small operator. Also, one jackass in the group can make a real mess of a driveway, becuase of his driving habits, jack rabbits starts and stops, etc. If you dig the hole, make the soft spot or ruts, you fix it. That’s a tough thing to teach city drivers.

 

[racookpe1978]

To get the speeder/rut-following/take-care-of-it-by-somebody-else syndrome to stop, you HAVE to get all three homeowners to share in the road repair cost.

Once THEY pay, THEY will police (self-correct and correct their children/guests) the problem causing the ruts. Then, AFTER the cause stops, a ten-year correction will actually last ten-years.

 

[emmgjld]

If you can get some fines worked in and windrow back & forth, some mag chloride sprayed on the lift surfaces and then lightly rolled is a typical solution on county roads here in Colorado. Similar to Oldestguy's discussion. (I know, mag chloride is a salt).

 

[dicksewerrat]

Mike,
do you have access to recycled concrete or asphalt? They spread well compact nicely and are easily renewed every once in a while.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com