Analysis of pile cap over laterally loaded single bored pile

[Stickherin4wd]

Hi,

My company has asked me to check whether the addition of a "pile cap footing" at the top of a laterally loaded bored pile (say 1500mm diameter) will help reduce the embedment length of the pile, due to poor soil conditions/water table/unstable excavation at design depth. The pile design depth is 9m deep. Previously, they have received advice, to add a 2400x2400x1000 deep cap to the top to reduce the depth for overturning.

My question is regarding the analysis of the "pile cap footing" working in tandem with the bored pile to reduce the pile depth? How should I be approaching this in design?

Thanks.

 

[Lomarandil]

Whether this works is very dependent on your soil profile.

The simple approach would be to consider it as a stepped bored pile, with diameter 2.4m over the top meter and 1.5m over the length, but neglecting any vertical effects. You probably won't get much benefit in that.

 

[dik]

The purpose of the cap is to strictly provide lateral resistance. Is it some kind of sign structure, in the open? The 1.5m shaft will not provide sufficient lateral restraint? Are the loads static? or transient? Do you have a geotechnical consultant on hand? A few questions.

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-Dik