Shale as driveway base 2

[Chaz7]

I have a 1000' driveway on raw land and the escavator is just about finished with the base. He is proposing Milify fabric, then a base of shale on top of 1st base. The reason for the shale is that when escavating, he discovers a shale "quarry" on my property and its using the shale for the primary base too. Instead of paying for runner crush, he is suggesting I use the shale on my property. Is the shale too soft for a a second course (approx 12")? In the spring after my house is built, he is suggesting putting a 1-2" coat of runner crush or millings (recycled ashphalt) on top of the shale. Does this sound OK? Also, soil is clay loam. One day I'd like to pave the driveway, but too expensive now.
Chaz

 

[dicksewerrat]

shale tends to soak up water, bothas rain,etc and from the atmosphere. With a clay subbase i guess i'd look for a better alternative. You mentioned recycled asphalt. That makes a good base and if it is hot in your locale, 6-8 inches of recycled will reset as a decent road. Just roll it in two lifts.

 

[Chaz7]

Thanks for the response! I'm in upstate NY, by Syracuse. Just to clarify,

A foot or two of initial base is Shale and clay mixture(topsoil was removed). The escavator proposes putting down Mirify on top of the initial base, then another 6-12" base of only shale (which I have on my property for free) on top of mirify, then 1-2" of runner crush or millings in the spring. So really, the final driveway won't be shale on top, but millings or runner crush. 6-8" of recycled would be almost $6000 in my area, plus $1000 to install. The escavator can lay down almost 12" of shale for about $3000. In the spring, it would cost me another $2000 or so to finish off with runner crush including labor. Bottom line, I'll save 2-3K using shale. Sound good?

 

[NewcastleEngineer]

My experience with shale fill is in the Ohio and Kentucky area. The problem with using shale in our area,as any kind of fill, is that the shale particles are not durable. If it is placed as a durable rock, in larger pieces, over time the shale will weather in-place when subjected to water and air. The intact pieces will soften and then the point-to-point contacts between the shale pieces will collapse causing subsidence. This is why the Kentucky Transportation Cabinet has spent millions of dollars studying how to properly place shale fills. Their conclusion is that the shale needs to be completely broken down into a soil-like mass using water and heavy equipment to avoid collapse of the intact shale structure.

If you are trying to use the shale as a granular base, the shale will not provide the support that a durable granular base would provide. Also using the Mirafi fabric will not prevent the shale from eventually collapsing.

I believe that using the shale will likely result in potholes in your driveway. Once you pave the drive, it will likely damage your asphalt pavement and cost you much more than what the recycled asphalt base will cost you. I believe a good durable base material will pay for itself in the long run, since it will reduce your long-term maintenance costs.

If possible you should talk with a local geotechnical engineer to determine if your local shales will behave as I have described. I believe they will, since shale is formed by compressed mud.

If you wanted to use the shale to build up a subgrade for your driveway, this is possible provided the shale is placed and properly compacted. Recompacted shales tend to give lower subgrade support values, due to posssible swelling characteristics. Again this would be a good thing to discuss with your local geotechnical engineer.

Finally, the geotextile fabric should be placed between the subgrade and the durable granular base material (i.e. crushed durable stone or recycled aphaltic concrete paement) to help prevent migration of the subgrade materials into the granular base materials and reducing the granular base support properties. If your existing subgrading is questionable the geotextile fabric could also help stabilize the subgrade soils.

Good luck.

 

[ebbnyc]

Hi Chaz, I'm doing research before laying my 2000' driveway, and noticed your post(s!) I'm upstate NY as well & thought I'd compare notes - had some bids come in that seemed real high and I'm in need of a second opinion!
If you catch this, you can contact me at ebbnyc@excite.com. If not, thanks anyway...
Regards,
Ben

 

[NASC]

Hi NewCastleEngineer,

Do you have any articles on the self-weight settlement of shale fills? I need to estimate settlement of some deep fills that are basically end-dumped blast rock spoil in the form of cobbles, gravel, sand, silt and clay from weak shale and moderately strong sandstone. There are lots of boulders too.

Thanks.

 

[cvg]

is this a private drive? what kind of traffic loading will you have?

 

[NewcastleEngineer]

NASC:

I do not have any articles on what you are looking for. Shale fills should not be placed as end dumped fills. The Kentucky Transportation Cabinet had problems with placing non-durable rock as end dumped fills. If your rock materials are not durable, you may want to reconsider how you place the rock fill.

 

[chimingin]

I have had very similar issues that I've been dealing with. I am closing a large parcel of land that has a pond on it. There is a dirt driveway approximately 900 feet long running along one side of the pond. At one time it was likely about 12 ft wide but since the property has not been in use for many years the driveway is now maybe seven to eight feet wide, has tire ruts, and some low points that are moist due to the closeness of the pond. There are also two RCP pipes slightly buried under the road to allow water that collects on one side to drain into the pond. I don't, for now, want to put in an asphalt driveway because it just doesn't seem to be a proper "fit" for the rustic-ness of the property. however, as with Chaz7 I'd like the option of covering whatever i do now, with asphalt some time in the future. At this point, I have received a price of $11,000 to widen the driveway to twelve feet, install a geotextile fabric and lay out nine inches of crushed shale. The location is the southern part of Renssalaer County, town of Nassau. The price comes out to almost exactly $1.00 per square foot. Any comments out there? I think my answers are already somewhere in the responses that have been posted.

 

[ebbnyc]

Hi Again - I'm still trying to solve a few questions definitively...

I've been told that using shale WITH a textile fabric is EQUAL to gravel in its ability to drain. True/False?

Shale in New York state (Ulster County) is harder, more coarse and larger than other parts of the contry and thus drains better than say, shale from Kentucky. True/False?

Shale's abilty to compact and maintain a crown, thus shedding water, is more important than it's abiltiy to drain - since you've got the textile under it. True/False?

Thanks for any help!
-Eric