I'm beginning a 700 ft driveway that will also be a designated fire access road. I need to be able to support a 40 ton fire truck and my geotech is telling me I need 7-10" of road base on top of a 95% compaction of the subgrade (Had a really crappy R-value come back, and I suspect I can get a better one with a different test). My question is, how does this sound for the subgrade... I have already scraped off the grass that's been sitting on this land for a long time. I was thinking of getting a crown on the road now, then ripping 12" deep, then coming back and compacting with a pad foot drum. Or, should I be looking at ripping first, compacting, then working on the crown and recompacting? In Northern California right now, we've had a little bit of rain here and there, currently I'm giving it about 1.5 weeks of drying out before trying any of this. It's not all clay, but it's a mix of gravel patches, brown clay, sandy clay and even some hard volcanic type rock structure on this hill. I'm new at this, and maybe I am wrong in thinking I can do this during the wet season? It's just tempting to try because we are looking at 2 weeks of sunny weather with a little bit of breeze and 60+ degree weather. I need to get a well drilled at the top of this hill that's a 10% grade in about a month and I want to be able to get a rig up there when the time comes.
Remove the sod, if have to use a ripper should already make compaction quality test. If designated Fire Access, the regional requirements will have to be met to meet their approvals and certification. Grade to 7" cut, Personally I would fill in with 2" and fines to a six inch depth then overlay with Inch Minus(fines) and Smooth roller or CTL compact the stone fill. Water as lay the top layer then allow to sit for a few weeks to develop a Crust, should be fine. My drive is close to 700', it is terraced at regular intervals(60-80') with culvert drainage from high side to the low side to preclude runoff degrading blow outs. It is Crowned to keep water along the Sides. Second photo is 2" minus, First is the 2" going down and trucks aiding compaction.
Besides the grass, you need to remove any further organic layer there before you start. Is that what you meant?
I did strip off the organics, probably need to take a little more off, but I am thinking I will take it down to crown it, and in doing so should remove enough. Here's a picture in its current state.
Do roads typically go all to crap around there in the wet season? What I am seeing does not indicate difficult road building conditions. A 40 ton anything is not going to be a problem. If they have a road specification to meet, do that. If you suspect that your soils test was not legit, get another. Undisturbed soil is very close to 100%. You can wet it and beat it if you want, but ripping it is a net loss game. 7~10" of base is long dollars. That's a county paved road kind of prep. An alternative to tossing lots of rock at it is geotextile. The link below meets California DOT specs. https://www.eastgatesupply.com/prod...2XrUBesR3LWY5XJPnDJLe6GoRSdt_23RoCFNsQAvD_BwE I doubt i is warranted, looking at your conditions. I see a road with a nice gradual slope, a little crown and ditches and let the water go left and right away from the road.
I lot of people have had great success using the geotextile fabric on driveways.
we used it on the national park job, on Stevens Canyon road. Dig down 3-5 feet in places, fabric and build back with CSBC.
Did you strip top soil?
The standard spec in my area is strip 4-6" inches depending on the soil bores, proof roll with a loaded tandem, undercut any soft spots, then rip the top 12" of existing soil, moisture condition and compact to either 95-98% density before placing any fill or finish grading.
I’m not sure what the extent is of top soil, possibly 24,” so no I have not stripped completely. this sounds about the same as what is recommended for this area. My main query is order of operation. Should I strip more, then crown, then compact?
I’m going to give the fabric a hard look. I like where you are at with the plan there.
I do deal with different soils here. Most of it is bony and glacially compacted. Once the organics are stripped the proof roll results are solid.
I covered thousands of square yards of geotextile fabric. We covered it with a lot of different materials, depending on the job specs. Recycled concrete, 3 inch crushed stone and fill dirt or fill grade gravel.. Some of the sub-base was very wet and soft. It was amazing how firm those combinations made a sub-grade. On narrow roads I would park a LPG D6 on the leading edge of the spread material. The trucks would dump right behind me and I would back up and over the pile to push it out on the fabric. Probably overkill for the OP's situation, but I thought someone else in a similar situation reading this thread could use the info.
I never knew they made a propane powered D6.
Tier 5!
Typing errors can create funny results !
As I'm trying to get my ducks in a row here for trying to make headway on this project this week, here is a better idea of what I am looking at doing. The natural water shed is all in the same general direction over this driveway. I plan on putting in a V ditch on the uphill side of the road throughout the whole thing, possibly running a culvert across at some point. Trying to figure out where that will work best. But does anyone have any tips? Normal crowning of about 3% sound ok for this?
Actually propane injection is used for more power in diesels.
It depends on how the ground typically takes water. Since this is a winter picture, my guess is that it does not puddle much if at all. The rip rap is likely way overkill. V-ditch both sides and bring the material in to build up and crown the road.
Yeah I see what you are saying with the rip rap. It looks like water doesn't sit anywhere, and almost the entire parcel flows down and to the middle (away from where this driveway is going), then a culvert takes everything under the street and keeps going.
go up there when it is raining hard and melting snow, and see how much water is in the culvert. There is your answer.
CP44 compactor ok, or should I rent a 54?
The little machine is big enough.
Really nasty white or grey clay regions here they use the geofabric, only do not drop so deep. Usually cut is just at a foot(+/-), fabric rolled out, 3"clean white rock overlay to a 8-10" depth then the 2"minus topped with either roll stone or inch minus crowned and raised from original grade. Makes a pave able surface if comeback with asphaltic concrete as drains well underneath. Still need to align culvert Cross Drainage to preclude blowouts. 3-4" clean for drain channel ditch floors.
Around here we'd just cut the topsoil off, place geotextile and bring in 4" minus rock for 6-8", and top with 4-6" of 3/4" minus. Make sure it's got crown, and cross drainage as required, but that's a pretty easy job. We do driveways with our 8ton shovel and a skid steer mounted roller.