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Improving a dirt/gravel road

Improving a dirt/gravel road

Improving a dirt/gravel road

I just found your site when I was looking for some information regarding improvement of an existing dirt/gravel toad that we use to get to our church. We have access through our county commissioner to some RAP (reclaimed asphalt) and there is oil sand available. My question is: can you lay RAP over the existing dirt/grave; road and then add the oil sand on top of the RAP? This road is used by oil tanker trucks and logging trucks, so it will have some heavy use and we have about 40 church members who come down the road 2 or 3 times a week. Our county commissioner says the RAP won't hold up under the oil trucks, but that the oil sand will. We can get the RAP basically for free, but the oil sand is very expensive. I'm concerned that we will spend a ton of money on the oil sand and then it won't last very long. We can't afford to spend much money on this project which is 2.1 miles of dirt/gravel road. Thanks for any input.

RE: Improving a dirt/gravel road

Not my area, but here's something I discovered in a different forum that might help. Gravel Roads.

RE: Improving a dirt/gravel road

Thanks very much to JedClampett and fel3 for the great information.

RE: Improving a dirt/gravel road


I had a few minutes this afternoon to edit my Excel spreadsheet template for gravel road design for general distribution. The spreadsheet follows the document that I linked to, which in turn follows the AASHTO (American Association of State Highway and Transportation Officials) procedure. The editing consisted of stripping out all references to the company that I work for. Since I built this spreadsheet years ago on my own time, it belongs to me and I can distribute it as I wish.)

I presume, based on the way you worded your question, that you are not a civil engineer. However, you may want to give this a go anyway. It requires getting some numbers from tables (as explained in the publication that I linked to) and to draw some lines on three nomographs (included in the spreadsheet), then plugging in the numbers and figuring out what works. Just don't formally practice civil engineering or the licensing bureaucrats will be after you (there are posts on this site on this topic). smile But, if you are successful, you will at least have an idea what your road actually requires. If you do have create a design for permitting purposes, then you will need a civil engineer licensed in your state. I have found that not many civil engineers know the AASTHO procedure, but a civil engineer who specializes in roads in general might and if not can certainly learn it quickly enough.

BTW, when I write spreadsheets, numbers in red are data, numbers in magenta are data that rarely (if ever) change, and results are in blue. The blue results are what the equations in those cells produce.

Good luck.

"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Improving a dirt/gravel road

fel3, thanks again for your help. That is an interesting and daunting spreadsheet. As you suggested, I am not an engineer, an accountant by trade. I'm hoping to assist our pastor in our efforts to improve the road we must travel to get to our church. It's an old church, established in 1893 and services are held in the same building as when it was established. I will carefully follow your instructions and hopefully develop some meaningful and useful data to discuss with our county commissioner. He is very agreeable to help us but unfortunately has limited funds to support the project.
Any information that we may be able to provide him will hopefully be useful in developing a project plan.
Thanks again,
Jay Dorrell

RE: Improving a dirt/gravel road

If it hasn’t been done already, the roadbed should be graded to promote drainage and ponding water. If the road has potholes, they really can’t be fixed until it dries out. If the drainage is poor, it doesn’t matter what you put on it.

RE: Improving a dirt/gravel road

Danielsgeo, Thank you for your input. The roadbed is in fairly good condition being that it is a dirt/gravel road It has some potholes due to heavy travel by oil tanker trucks and logging trucks. All grading for drainage and to smooth the road are done by the county commissioner, so I have to presume that issue has been addressed. If the roadbed is properly prepared, would the RAP with the oil sand be an improvement over just oil sand to pave the road? We can get the RAP basically for free but the oil sand is very expensive. If the RAP would improve the life and durability of the road once the oil sand is applied over the RAP, then that is an option we may consider. I just have no idea if that procedure is feasible and worth the effort.
Thanks again,

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