Minipiles versus pipe piles 1

[jakin]

To support a structural foundation slab within a building with very limited headroom, specs call for minipiles (1-3/4" Dywidag rod in 5-1/2" hole); tolerance of max 2% to vertical. Soil is 18' dense fill, 20' very soft to soft clay, and medium to stiff clay down to hardpan at 90' depth. Contractor proposes change to concrete-filled segmental pipe piles (including 5-1/2" and 3-1/2" diameter). I am concerned about the proposed substitution. Any ideas?

 

[BigH]

I personally would not have a problem with the contractor's solution using the 5.5" piles - this is a pipe pile of similar tip diameter to long timber piles. You didn't say if open or closed tip - I'd use the latter. But at the depth of 90 ft, you'll need to check the mode of buckling. The smaller size, well, it just seems too small!