private driveway

[waldo15]

I'm in the process of building a private driveway for my personal use. My problem is that I have a wet area that is about 60 foot long that I have to cross and I can't go around it. My question is, should I "de-muck" this area (and if so how much should I take out) and what should I fill the de-mucked area with? The range of responses that I've gotten include: de-mucking as little as possible, de-muck until you hit good soil, fill the de-mucked area with rip-rap, or surge stone, or crush and run, or compactable clay. I have hand augered the area in question and after 6 feet there still doesn't seem to be "good soil". I plan to get this area passable and put 2-3 inches of No. 4 gravel or GAB on the surface. I would like to let the road settle for about one year before having asphalt poured as the final cover. I'm planning for the remainder of the driveway to be built up with six inches of compactable clay before adding asphalt. Your suggesting would be appreciated.

 

[Maury]

Using the drive for a year should tell you if it's going to hold up in an acceptable manner. You'll have to make a judgement call as to the cost of repair over the life of the drive vs. excavation and replacement now. I'm concerned about your selection of material thickness. 2" - 3" of gravel isn't going to be of any use to bridge a soft area. I suggest a minimum of 8" of gravel or crushed stone over a layer of geotextile fabric. For the rest of the drive, placing an asphalt surface directly over clay is something I've never seen done. I can't imagine not using aggregate base, typically 6" thick. Also, check the drainage in the area. Maybe some re-grading or underdrains can help.

 

[snafuman]

In similar situations, we have dumped large rock (sometimes alot!) into the muck, then covered with geotextile fabric, then aggregate base; or we might place drain rock over the fabric, then more fabric then aggregate base. You may be able to us geotextile alone with a geotechnical "webbing" filled with drain rock or aggregate base. If its just a private drive your loads are too high. This kind of thing is a judgement call and also depends on what materials you have available cheaply (if you have lots of cheap rock, dump away!). If you can drive across it at all now, the geotextile with base may be enough. For us, alot of the time these decisions have been a judgement call made in the field, based on how bad the area is pumping, sometimes based upon what materials are locally or quickly available.

If you have 6+ feet of this stuff, it would probably cost you alot more than you want to spend to dig it all out and replace it.

Might want to go heavier on your base than 2-3". Also don't understand why you would want clay between your base and pavement.

 

[gtrainor]

I'm no expert at it, but some of the contractors I know use "Lime Stabilization" in gooey soils. Check out a local paving contractor or municipal agency to see if they use it in your region. Check out:

http://gulliver.trb.org/publications/millennium/00016.pdf

 

[Focht3]

Where is your site? (Country, state/province, city.) Are the soils considered to be clays, silts or sands? Are the local roads predominantly asphaltic or Portland cement concrete?

Applying hydrated lime may help, but it has to be mixed in to be really effective. If the soils are very silty, then Class C fly ash is better. Again, mixing is required. Whatever you do, do not use quicklime. It's too dangerous to work with -

[blue]Maury[/blue] and [blue]snafuman[/blue] provided excellent comments. Unless you have access to an agricultural discing unit available to you for mixing the soils, I'd go with the geotextile/clean stone/crushed rock/asphalt approach. The geotextile and clean stone will allow for drainage of the wet soils - be sure and give the collected water a place to go! And expect to redo the asphalt wearing surface in about a year. This section will probably require more maintenance for many years to come...



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[KRSServices]

This "wet" area you describe sounds suspiciously similar to what one would find as a pond or marshy area, where surface runoff would collect. I understand it is only a driveway, but my question is a bit more preliminary and referes to the existing condition. Is there an existing trail or driveway on the proposed alignment now? If so, how is it behaving, particularly when we, or in the springtime (esp. if there is frost)? When you augered to the depth of 6', you stated that you did not find "good" soil. Is the material a saturated clay, perhaps blue or greyish in colour?

Based on what you have written and certainly before going through the expense of asphalting the drive, I would suggest spending a minor amount of money and hiring a local civil or geotech engineer to visit the site and provide a recommendation that you can take to the bank and a contractor.

KRS Services

http://www.krs-services.com

 

[waldo15]

I am a first time subscriber to eng-tips and I must say that I'm very please with the responses to my problem. To add a little more detail, I live in Central GA. The vast majority of roads have a compacted clay layer under either asphalt or concrete. Let me respond to some of your questions. MAURY: I did a poor job of explaining the 2 to 3 inches or gravel. What I ment to say was that after I make this wet spot passable for vehicles (using soil and/or rock), I plan to add a 2 to 3 inch layer of #4 gravel or GAB (graded aggregate base) on top in order to smooth the road out and make driving on it less bumpy. SNAFUMAN: In your third sentence, didn't you mean that since it's just a driveway, my loads would NOT be too high? FOCHT3: The roads in my area are asphaltic. I also have access to a tractor with disc. KRSSERVICE: Yes, this area does receive some minor runoff but also has a seasonally high water table that is about 12 from the surface. Yes, there is an existing dirt road where I propose to put the driveway. The majority of the road does not exhibit the problems of this area. The majority of the road is passable year-round. Yes, the material from about 1-foot down shows signs of saturation (i.e. gray and/or mottled).

I have spoken to 2 county road superintendents and one said to de-muck the area and then fill in the area with clay. Another said to add rip-rap or surge stone, then #4 or GAB stone on top.

To my way of thinking, and that surely doesn't make it correct, the more the area is de-mucked (i.e. going below the ground contour) the closer I get to the water table. It seems to me that it would would be better to use geo-textile and stone over the exist ground surface, even if it is muddy and build the road up and additional 6-12 inches above the existing ground level. What good does it do me to place dry clay in an area where wet clay was just removed? Lastly, a few people have told me that placing rock (either rip-rap or surge stone) would only having the rock disappear into the mud (presumably, never to be seen again, except maybe in China). Is that possible? If I used a Geo-textile, would that prevent the rock from sinking into the mud? Would driving over the geo-textile and rock cause the rock to puncture the geo-textile? If I want the driveway to be 10-12 feet wide, would the geo-textile have to be 14-15 feet wide to allow for sagging into the mud? Does geo-textile come in this width and if not, how do you join the pieces together?

Again, the consistency of your answers has gone a long way in clearing up the cloud of misinformation I've received.

 

[Focht3]

If you use a good quality geotextile then the rock shouldn't perforate it. I like Mirafi (

http://www.mirafi.com),

but other manufacturers make good products, too. I would start with at least a Mirafi 170N if your rock is from a "hard rock" source and you put it directly against the geotextile. Our local rock is a crushed limestone, so we can get away with a 160N, or even 140N.

As the water drains from the "muck", the soil portion gets stronger and more dense. The pavement will settle some as a result. If you go this way, you might put the geotextile down and cover it with 4 inches of clean stone, topped with 8 inches of crushed rock. (The clean stone is usually a washed river gravel that is sub-rounded in shape, and won't puncture the geotextile.) Cover the clean stone with 8 inches of crushed rock. The clean stone will act as a drain, allowing the muck to be "dewatered" relatively quickly.

Don't put your asphalt wearing surface in for at least 2 or 3 months. (At this point, I'd wait until March.) Add crushed rock as necessary to maintain a "level" road surface.



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[snafuman]

er' yes, as the politicians would say, I "mis-spoke", your loads "are not" that high.

yeah, like I said in the first post, sometime you can dump a lot of rock into one of these mucky spots before it starts to firm up, and it can get expensive, especially if rock is not locally and cheaply available.

just another thought, or option, you may consider a rigid slab over your surface instead of asphalt. A reinforced concrete slab will spread loads out to the point where your poor soils, with a little help from geotextiles as others have suggested, may be enough to support your loads. Like every solution, it costs more, but may be less expensive than other solutions.

don't understand why anyone would tell you to muck your soil out and replace it with clay. Most clays I've seen pump badly when wet. Read in your post that roads in your area are constructed with a clay base, very interesting...

 

[layfieldman]

Waldo, Focht3 suggested using the 170N which is a non-woven geotextile with very good drainage properties and is available in 15 foot width rolls. You probably wouldn't use up a whole roll but they are not very expensive. The material is like a thick felt and is fairly difficult to puncture. It offers the functions of separation, reinforcement (not very much at 180 lbs ultimate strength) and filtration. I may sound like a sales person but I'm not. I'm just in the geosynthetics industry (applications engineer for soil reinforcement) and have access to alot of information. If you have any specific questions about geotextiles please don't hesitate to ask.

 

[KRSServices]

Waldo,

Thank you for confirming my my concerns. I would be careful with the advice of the superintendents due to the fact that I have hired and fired my share of these folks. While many may be very knowledgable in thier field, many others are not, due to the manner in which advancements occur. Case in point, you describe the water table as being 12" below the existing surface. Wet/saturated clays will equal needless expense if you do not properly take care of the subgrade and base first. If the ewater table is indeed that high, it will only be a matter of time before any imported clays become saturated and your surface will fail. Also, I am also convinced that many of the responses, concerning placement of the fabric are right on the money.

Speaking of money, I suggest you hire a local civil or geotech engineer and have him/her prepare you a proper report and recommendations. You will find it very specific and you will then have a very reliable driveway which will not be prone to failure.

KRS Services

http://www.krs-services.com

 

[waldo15]

Great info. folks. I'm doing my research on geo-textiles and looking into civil and geotech. engineers. I'll keep you posted on what I find out. What a great web site.