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ρ as1 FOUNDATION REQUIREMENTS (ALLOWABLE SETTLEMENT): What is a foundation? Two definitions: o Structural: o Geotechnical: Two basic classifications: 1. Shallow: 2. Deep: Strip (walls) Spread (columns) Combined (unify support) Strap (shear & moment) Mat or Raft (minimize differential ρ , trade-off between formwork & materials) Drilled Shafts or Caissons (economy, heavy loads) Driven Piles (quality control) Auger Cast, Stone columns (economical, light loads)
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ρ as2 Criteria For A Satisfactory Foundation: 1. Consider any future influences such as construction, drainage, excavation, etc. 2. Provide adequate bearing capacity to avoid catastrophic bearing or punching failure. 3. Control settlement to prevent structural damage and impairment of design function. 1. Future Influences o Frost Action s Heave due to freezing, sudden drop due to thawing. s Find maximum frost depth from map (USDA or from local experience) s Footing should be below frost depth in fine grained soils, 75% of frost depth in sands. o Clays with High Volume Change Potential s Volume change due to shrink or swell with change in water content - function of soil mineralogy (Montmorillonite and Attapulgite very susceptible). s Movement greatest under perimeter of structure. s In arid regions the soil is dry and may get swell from leaking pipes, irrigation, etc. (eliminate water source and get shrinkage!). s In humid regions the soil is moist and may get drying from drought, poorly insulated furnaces, etc. which cause shrinkage. Desiccation may also be due to trees or shrubs. s
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This note was uploaded on 09/12/2011 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.

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