Shale as driveway base
Shale as driveway base
(OP)
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
Chaz





RE: Shale as driveway base
RE: Shale as driveway base
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?
RE: Shale as driveway base
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.
RE: Shale as driveway base
If you catch this, you can contact me at ebbnyc@excite.com. If not, thanks anyway...
Regards,
Ben
RE: Shale as driveway base
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.
RE: Shale as driveway base
RE: Shale as driveway base
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.
RE: Shale as driveway base
RE: Shale as driveway base
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