I am building on a property where the engineer designed the footing to be of pier and beam design with the pier being about 2m deep. The soil report actually recommended the use of screw steel piles because water was found in particular one of the bore hole where it came in quickly (the other two water came in slowly).
After quite a bit of reading, I do prefer concrete piers over steel screw piles as the foundation method but it seems there might be some problems when trying to put them in due to bore holes possibly collapsing. A couple of builders I talked to are saying that screw piles will be the way to go but it seems like they say that because it's the easier for them. Ont he other hand, I asked the engineer again and he still thinks that concrete pier is the way to go. This includes my uncle who is also a structural engineer. I called up foundation companies and they prefer concrete piers also.
What would people do in this case? I have to put in about 40 piers of 400m thickness. I got a few quotes done and going concrete piers would be around $8-10K while steel screw piles will range from 11k to 15k (because they have to go down to 5m based on experience within the area of this piling company).
The soil profile is something like this:
0 < 1m : Brown and Grey silt clay sand FILL (loose)
1m < 2m Dark Grey black silty sand (loose)
> 2m: Light Grey brown sandy clay (medium density to stiff - very stiff)
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