A fire company contacted me to make a driveway to there back building which stores their ladder truck with a weight of 60,000 pounds. There current asphalt parking lot crumbled and now has ruts to the axles of the truck. The dimensions is 14' wide by 65' long and a apron addition of a 25' long by 15 wide triangle. What depth do i need to go with so the truck doesn't sink, i was thinking of 6 inches of 3's and compact it and then 6 inches of 2b modified and compact. is that enough base? thanks
Two approaches, find out what the soil is underneath and engineer it from scratch, or find out what is underneath the failed current paving and go from there. I doubt that's enough, most of that 60k is on two close axles, quite a challenge to support, but I'm not an excavation contractor or engineer (soils, civil or otherwise).
Like Delmer said, if the asphalt failed then your problem lies in what's underneath. You may have just some bad fill or there may be a water problem that needs addressed first. If its just bad ground I would dig down and remove the bad fill, then lay down some geo-tech and compact in to within 8" of finish grade. Lay down a layer of #4's and a 2" layer a 2a modified on top. If you can it would also not be bad idea to install a under drain to keep this from happening again but some times that's not possible.
From what i see the parking lot was never deisgned for the fire truck, it was a back parking lot for cars and then they bought a used ladder truck and erected a steel building behind the fire hall. From what it looks like it was a 2" or so lay of asphalt and it lasted with the very minimal car load but cant withstand the new load of the truck.
Also its a single rear axle which is odd to me for that weight.
Dig it out and pound in 2' of baserock tight as hell, top dress with some clean rock and your done. Pj
Probably a miss quote of weight … or there are more than 2 axles for the whole rig right/wrong ??? to get that kind of a weight figure …… Anyways, I built a parking turnaround area c/w a 200 meter long entrance driveway at my/our local Fire hall …. the new additional hall we had built was for 3 apparatuses, 2-Engines/pumpers and our Tank tender …… The contract involved removing and building a supportable "Year-Round" accessible base …. where we are, we have to deal with winters (like starting now) and ending when "Break-Up" is completed (that's when the Frost is coming out of the ground in the traveled drive area, as much as 3-6' deep, things get really really soft) usually in April/May ….. the area had to support our trucks no matter what !!! …. I started by digging out 3' deep, slopping the base 2% away from the foundation ….. (oh, btw, our building codes here call for footing depth to be at min 42") ….. I laid down a total of 1000 yds, first was 2' compacted progressively and adding water to achieve ~ 95-98% proctor (using my Bcat with the Allied Skid-Pac, we had a thread here on HEF discussing that) …. using a 3"minus screened pit-run material maintaining the top to the original start of 2% grade …… we then laid out a woven heavy gauge geotextile 12' wide rolls, the geotextile prevents the soft muddy stuff from hydraulicing up to the surface as well it allows all moisture to go down and stay down, once it's down there it'll follow the grade away, then again added another 12" of the 3" minus compacted (also to the 95-98%) ……. I topped it off with ~6" of a crushed 1" minus Road-Mulch material, also compacted. That was ~4 yrs ago, that's 3 winters ago and when we roll out the heavy s/a engine, with 800gal of water and equipment on board, during "Break-Up" it does NOT even leave a 1/2" foot print, basically just the tire print, there is more damage done by the rookies dry steering the trucks when turning to back into the hall ….. Proven Success !!! Now IF ONLY I can get the picture re-sizer to work i'd post the pics !
The problem around here is stone cost. You can find good compactable fill a lot easier and a lot cheaper then trucking in stone. Around here a tri-axel load is about 23 ton and will run you between 500-650 a load.
Something else to consider - are you getting paid to engineer this? From what I am reading they are wanting you to give them a durable driveway but don't have any information about the sub-soil conditions or any recommendations for materials. Now I am not saying you have to be an engineer to do this job, my point is about liability. If you are engineering this project then you need to get paid for that. If you come up with a solution, install it and it doesn't hold up they will be coming back to you to fix it and you will have no help, or in the world of commercial construction, a finger to point to someone else who designed it. Just a thought.:cool2
WOW !!! …. that sure sounds Pricey !!! …. The big problem with a compactable fill material is usually it has NO permability (won't let the surface introduced water soak thru it… LOL) ….. Can you really put a price on an Emergency Vehicle not being able to leave the Hall ???? …….. "UHHHH Sorry that u'r House burned Down Mam !! … But the Fire truck got Stuck in the Driveway" ………. Hmmmm ???? … "FAIL" …… LOL
Well the first thing you have to do is keep it dry, water is your enemy. Next you need to spread the load out, think about using geo textile fabric. Next thing you need is large stone, 4 or 6" minus, probably 2' deep at a minimum, then just enough 2" minus so you can grade it. That being said, CM has a very valid point, if it fails there are no winners.
I've seen ladder trucks that weigh real close to that on two axels. The tower at the department I work at weighs 80,800 on three axels. If memory serves Washington, D.C. Bought a ladder truck on two axels that was known to damage the roads due to its weight.
Have you priced out crushed concrete as a sub-base? I wouldn't get too hung up on the cost of stone. Price the job out the way it needs to be done. The price of the job will be forgotten with time. If the driveway fails, they'll remember your name all too well.
The price of the job will be forgotten with time. If the driveway fails, they'll remember your name all too well.[/QUOTE] Well said! I tell my crew that all the time.