155_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

155_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 -...

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DF35 Pile "Setup" o pile capacity changes (generally increases) with time after a pile is driven (thixotropic) o generally a result of change in side shear, not end bearing o increase in capacity known as setup or freeze, occurs in most soils, very significant in clay o in short term: setup is a result of pore pressure dissipation resulting in stronger soils with greater horizontal stress increase o in long term: setup may be a result of "aging" effects - creep under constant stress o decrease in capacity known as relaxation, occurs in shale, very dense, fine sands and some highly OC clays which develop negative pore pressures (dilate) during driving and a temporary increase in penetration resistance which dissipates with time (fairly unusual fortunately) o pile capacity measurements occur at a given time, so setup should be considered o check setup with "set checks", redrlve pile after 15 minutes, 24-72 hours and load test (for comparison) o best to use a PDA and CAPWAP for set checks - hammers behave differently at start up,
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This note was uploaded on 02/10/2012 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.

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