Exposed road base - driveway construction question

[PILOON]

You say a clay base. When that gets wet it will want to ooze out in the center.
Think snow shoes.
Geotextile will act like a snowshoe and spread the loads without letting wet clay ooze out up into the center.
Even our county is using textile now under road base.
I know of one guy that used old synthetic carpeting in lieu of geotextile with good results.
The textile will allow water to be pushed out but not the soils.

 

[BigBassBrent]

You say a clay base. When that gets wet it will want to ooze out in the center.
Think snow shoes.
Geotextile will act like a snowshoe and spread the loads without letting wet clay ooze out up into the center.
Even our county is using textile now under road base.
I know of one guy that used old synthetic carpeting in lieu of geotextile with good results.
The textile will allow water to be pushed out but not the soils.

With the soil we have it was almost a no brainer to go with the geotextile! I liked your snowshoe analogy. Thanks.

 

[EddieWalker]

I was hoping I could get some help planning my driveway construction. Searching didn稚 produce any answers to my specific situation but I read many posts about road construction and gained some great knowledge. Thanks TBN.

The initial portion of our driveway is going to be 12' x 200' and travels downhill at a 4-5% slope. The soil is high clay content and has a pretty high rate of shrink / swell. (So the soil reports says.)

For the road subbase, we will remove top soil down to 8 which is where the red clay begins. After the subbase is leveled and compacted we will be installing geotextile woven fabric. Then we will put 8 of 3肺1 crushed limestone for the road base. There is no fine materials in this rock. It will initially be compacted with loaded vehicles. My plan is to get this portion of road built so we can begin construction of the home site.

We hope to leave the road like this (no top coat) for the heavy construction equipment to drive on. Once construction is complete (could be up to a year) we plan to come back, add more base rock to any low spots, reshape, then add 4 of top coat gravel. For the top coat plan to use a 1 3/4" limestone road base aggregate (called city base in my area) containing a lot of fines. I may come back later and add a layer of small limestone gravel for apperance.

My question is, will I be doing any harm to my subgrade and road base by leaving it exposed to rain during home construction? Without the top coat, the water will easily enter the rock base and permeate the subbase. To help with drainage during this time, I plan to put a temporary drainage ditch at the end of the road so that water that makes it to the subbase will drain out and not collect.

Is this an OK plan or should I install a top coat before the big trucks drive on it?

Sorry for the long post, lots to explain. Thanks for any help.

Added a pic since everything is better with pics~
View attachment 410932

DO NOT REMOVE soil with plans on filling it with rock. All you are doing is creating a place for water to sit. Removing top soil is when you have soft, loamy soil that will drain water and settle over time. With clay, you need to build up your clay road to get it above the surrounding land. Drainage is the most important part of building a road that will last. You can dig trenches on the sides of the road to get the soil, or you can haul it in.

Once you get that soil spread, IT HAS to be compacted. This is a very important step that seems to be forgotten, or not understood. If the soil is not compacted, it will hold water and be a muddy mess. Compacting should be done by a roller. Do not expect a tractor or truck to have enough weight to do this unless you are willing to keep driving over it for months before putting rock on it. This might be a good idea with construction going on. Build up the clay and keep fixing it until it's compact.

The gravel needs to have jagged edges and vary in size from a couple inches down to fines. The jagged edges are very important because that's what locks it all together. The fines fill in the spaces and form a water tight barrier that will support heavy vehicle traffic and shed rain. It has to be at least four inches thick. Six is better. If it's not thick enough, it will wear and develop pot holes.

Getting it compacted is also very difficult. Easiest way is to just wait for a big rain and then drive over it after it's soaked. Once it dries out, it becomes solid.

Be careful of advice from people in other parts of the country. What works there isn't how it's done here.

Eddie

 

[BigBassBrent]

Thanks Eddie. We actually do have very soft loamy top soil. Already stuck the truck once. :ashamed: Once we go down about 8" we hit the red clay.

The revised plan is to remove 8" of top soil to get down to the red clay and lay the geotextile. Then we plan to install and compact 10" of road base that is used by the city here. This would bring the road surface up 2" above grade. Proper shoulders and ditches should keep the water from making it under the geotextile. Is my assumption wrong?

Here is one of the test holes I dug and a chunk of the clay found at 8".


-Brent

 

[GLyford]

Okay, New England logic here, so I may be way off base...but I always think of gravel, packed or not, as being more permeable than clay. So it sounds like you're planning to remove your upper "sponge" layer and stop when you reach the clay.

It would be more work, but what if you remove your topsoil all the way across both your ditches, too? Then take an inch or several of the clay from the ditches, and pile and pack it on your roadway with a crown, so that this water resistant layer has both a slope and a ditch to go to. Then put your fabric and gravel on that to support the vehicle weight now that the under layer is managing the water?

It's also just as likely that a water filled channel in the clay on either side of the road would be almost as bad as a channel in the middle of clay under your roadway, but as you are currently describing it, you plan to stop at the clay layer and not dig into it to put in your roadway. I think several of us were initially picturing your road being cut into the clay and then filled with gravel...pretty much making the road a low spot where water would collect.

If I'm reading Eddies comments correctly, he may even be saying that if you pile and grade the clay correctly, you won't need the gravel...?

 

[BigBassBrent]

I think understand what Eddie is saying about creating a ditch full of rocks. Makes perfect sense. He may have missed the part about me deciding not to use the raw crushed rock anymore. I changed my mind and decided to use a local road base aggregate to build up the entire road to 10" which will be 2" above grade. This should be impermeable after compacting and keep the clay subbase dry. I think it's also important to remember that I am going down a 4-5% grade which will allow me to use shallow ditches and should easily keep the water flowing downhill. I think my biggest challenge on this downhill road will be ensuring a proper crown so the water does not run down hill on the driveway surface and wash it out.

My lack of experience tells me that I am probably wrong about most this though. LOL

 

[xzcVAbc5]

This may be of some interest. The military makes publications necessary for the functions they do.

See chapter 7: http://armypubs.army.mil/doctrine/dr_pubs/dr_a/pdf/fm3_34x400.pdf

Also this manual: http://armypubs.army.mil/doctrine/DR_pubs/dr_a/pdf/fm5_430_00_1.pdf

If you want more Google "road building military fm". FM stands for "Field Manual".

 

[BigBassBrent]

This may be of some interest. The military makes publications necessary for the functions they do.

See chapter 7: http://armypubs.army.mil/doctrine/dr_pubs/dr_a/pdf/fm3_34x400.pdf

Also this manual: http://armypubs.army.mil/doctrine/DR_pubs/dr_a/pdf/fm5_430_00_1.pdf

If you want more Google "road building military fm". FM stands for "Field Manual".

Thanks for this.

 

[BigBassBrent]

We (dad and I) got a little work done on the road this weekend before the rain started. We heard from the county about the culvert on Friday. No culvert required for our 24' turn it. We were told we could install a dip driveway. When I asked what that was he just said cut off the high spot on the back of the ditch and lay rock to the road. Excellent news since I was concerned about the concrete trucks crushing the culvert.

We used the 33hp kubota and the 6' box blade to get the road subbase going. We did not remove all the topsoil. Only the organic stuff. We measured and marked everything so we could get started. We measured the slope with a line level and got 4%. We ran the surface several times with the bb rippers fully extended. We dumped most of the removed material since it was full of organic stuff. Then we ran the box blade with no rippers for quite a while and moved material to low spots. Between running the box blade we compacted with the truck. The soil seemed to have perfect moisture for compacting other than a couple of soft spots. Here is what it looked like Saturday night when we left.

On day two we had to do some cut and fill with the bucket to try and make a steady slope since trying to move it with the box blade was taking a long time. We cut half the ditches with the box blade set to an angle. It worked well but we went too deep in a few of the softer spots. We will fix that later. I still need to go back and make a transition on the outside of the ditch but we ran out of time. All in all, phase one is going well. (Day two pic)

We still need to build up the road subabse and shape it, then drive on it for a month or so to get it nice and compacted. Then we will lay the geotextile and road base. Overall, I am pleased with the results so far. Thanks again to everyone who posted advice. It has all be helpful in one way or another.

 

[Cord]

You're plan is sound, but I'd make a couple of modifications. I couldn't read what you were planning using for the base, but it should be a coarse produce. 3-4" is excellent. Now this product is very hard on tires. The contractors are OK with this, but your car will hate it. My local quarry has 3" TB (traffic bond) which has fines in it. The fines do help stabilize the rocks so they're not as abrasive. This stuff doesn't make for a bad driveway, especially for construction traffic. I feel that with expansive clay, the 4" base is a bit on the thin side. I'd suggest increasing this to 6" and keeping the 4" top coat. The 1-3/4" top coat is a bit coarse. Personally, I wouldn't use anything coarser than 1-1/4".

When you are at the point of the temporary base the driveway will be low and will catch water. Be sure to provide a aggressive crown and provide opportunities for the water to escape.