pre-cast piles spacing

[shei]

I'm currently doing a design for the foundation of a six storey building using pre-cast concrete square piles 0.45m x 0.45m x 18.2m long. I have searched through several references and found out that the required spacing ranges from 2 to 3 times the diagonal dimension of the pile.

I would like to know what is the maximum allowable spacing for the piles?

Thanks and best regards.

 

[Ron]

The maximum spacing depends on your loads, how you will support the loads between the major column/wall loads (are you connecting pile caps with grade beams or will the foundation include a pile-supported mat), the compression capacity of the pile, and the tension capacity of the pile, if needed for overturning or uplift.

 

[BigH]

As an addendum to my colleague Ron, I have used pile spacings in the order of 10 or more with the piles being connected by a grade beam. Why so far apart? I had 25 ft of soft clay, 10 ft of compact sand and >100 ft of soft clay. I was founding the piles in the sand and I wanted the spacing large enough so that there would be no overlap of stresses that could be transmitted as a "group" to the clay below. It worked; haven't heard "boo" from anyone for 13 years.