Deep Foundations (Piles & Caissons)
CSI Division 31, Earthwork
Foundation systems, driven piles, drilled caissons or shafts, or similar deep elements, that transfer a structure's load down through weak or unstable near-surface soil to a stronger bearing layer or bedrock well below the surface, used when a shallow spread footing foundation can't provide adequate bearing capacity for the site's actual soil conditions.
Why it matters
Choosing between pile types, driven versus drilled, and confirming actual capacity depends heavily on site-specific geotechnical data and often requires field verification, such as a pile load test, since a deep foundation that doesn't reach adequate bearing capacity fails in a way that's extremely expensive to correct once the structure above it is built.
On a real project
A high-rise's structural engineer specifies drilled caissons extending to bedrock, sized and verified through a pile load test performed on a sacrificial test pile before production piles are installed across the site.
Who this matters most to
A Deep Foundation / Pile-Driving Specialist operates the specialized equipment that installs piles or drilled shafts. A Structural Engineer designs the foundation system based on the site's geotechnical report.
Where this goes wrong
A contractor installs driven piles to the depth shown on the original drawings without confirming each pile actually reaches the required bearing capacity through driving resistance measurements. Several piles refuse well short of the specified depth, and the discrepancy isn't investigated until post-installation testing reveals a foundation that doesn't meet its design capacity, requiring supplemental piles to be added.