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Drilled underreamed piers with eccentric loads

Drilled underreamed piers with eccentric loads

Drilled underreamed piers with eccentric loads

(OP)
Can anyone point me in the direction of a good resource for checking drilled, underreamed piers subjected to heavy vertical gravity loads that are eccentric to the centerline of the piers? (no lateral loads... just eccentric vertical loads).

The piers are not too deep, 12 ft to 16 ft range, and have fairly large bells due to lower soil bearing capacity at tip (2 ft to 3 ft shafts and 4 ft to 7 ft bells). The eccentricities are not severe, but need to be properly evaluated in terms of making sure the soils can handle the loads. Not worried about the piers themselves in terms of strength.

Checking eccentric vertical loads would seem simple if just using P/A+ M/S like a simple spread footing. However, this approach seems excessive since it ignores passive soil pressure. On the other side of the coin, Brom's method and other pole footing approaches seem inappropriate due to the shallow depth and large bell. Hence, I believe I am somewhere in-between!

Any thoughts or guidance would be appreciated!

RE: Drilled underreamed piers with eccentric loads

You may convert the eccentricity and the gravity load to a moment. You can then analyze it as a free headed pier subject to a moment. Be careful with the signs. Roark's formulas has a beam on elastic foundation subject to a moment at its end. From here you can get soil pressure, shear, moment, slope and deflection. Foundation Design by Cernica, pp 256-257 also has the same equations.

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