Helical pier vs. Driving Concrete Piles
Helical pier vs. Driving Concrete Piles
(OP)
I am going to be building a new house bordering a manmade canal in florida. The lots were constructed with poor fill. Typical houses in the area are built with 10"x10" conc piles driven to 15 ton capacity, about 12' on center, grade beams, and block walls. I am considering using helical piles instead of driving piles. I think helical piles are more cost effective and are less disturbing to neighbors. Any thoughts?






RE: Helical pier vs. Driving Concrete Piles
www.PeirceEngineering.com
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
look at galvanizeit.org for some reference material on galvanised steel corrosion rates in salt water soils.
It can be done but it needs to be very carefully managed.
Personally I would agreed that concrete piles are probably better but I would be concerned about maintenance of cover around the reinforcement.
Precast driven piles is definately a safer more durable option.
RE: Helical pier vs. Driving Concrete Piles
Pre-cast concrete pile still have steel in them that can and probably will corrode. Axial capacity-wise, you can get a lot out of helical piles and they will be much cheaper to install. I understand the others concerns regarding corrosion, you can definitely get galvanized augers and pipe...
Now if your house is going to be a stilt-type house, then a concrete pile that will cantilever above grade to form the building columns is a good option. I have used that before on a bay in SW Florida where storm surge scour was a huge issue.
HTH,
Andrew Kester, PE
Florida
RE: Helical pier vs. Driving Concrete Piles
I was talking with a pile driving company who drove pilings for the neighboring propertys. He said the soil is muck down to about 45-50 feet then bedrock. He said helical piles in this situaion would cost 3 times more than driving piles.
Sounds like driving conc piles is the best option.
RE: Helical pier vs. Driving Concrete Piles
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Helical pier vs. Driving Concrete Piles
www.PeirceEngineering.com
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
What county are you in?
Have you had SPTs drilled on your site?
40-50 ft of muck over limestone would be very surprising, so say my coworkers (geologists). My point is to take a contractor's opinion with a grain of salt, like asking a roofer if you need a new roof...
Helicals can be installed down 50+ ft into limestone no problem, actually, with a lot of clay it can be an issue in penetrating through the clay layers. Depending on your area it has been done for less than $2000/helical, also depending on the depth to limestone. Depending on the model and company, I have seen 20k++ axial allowable capacity.
Mike is right, this is a specialty. But there are areas of Florida where there are a lot of these types of contractors because of residential foundation repairs due to soil issues.
PEinc also has a valid point on the lateral buckling stability of a 3" steel pipe driven down 50ft. We've discussed that in our office before, not a lot of good technical info out there on that. How much lateral support does soil (especially organics) at various depths provide? Unsure, may involve on-site load testing to know for sure.
That's about all I know, HTH!
Andrew Kester, PE
Florida
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
www.PeirceEngineering.com
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
1.45/1.59^2 = 0.57 >50,000^2/(4*75*30,000,000) = 0.28
A consideration for driven piles would be is there access to bring in equipment and 50' piles? Will the neighbors call the police to stop the disturbance the first time the hammer hits? If a diesel hammer will it spot the neighbor's car or house?
RE: Helical pier vs. Driving Concrete Piles
RE: Helical pier vs. Driving Concrete Piles
The Tampa area has a lot of helical and "Push-pin" pile contractors that may serve that area with a local contractor.
Good luck!
Andrew