11/22/2017
Sub and Deep Foundation Systems
Caissons
•Shallow •Deep Auger Cast Piles
Mat and Raft Foundations (1)
• Entire building is placed on a large continuous footing ▫ Thick flat concrete slab with heavy steel reinforcement • Used to spread the load from structure over a large area • Reduces differential settlements ▫ Concrete slab resists
Geopier
Piles
•H Piles •Wood Piles •Franki Piles Interior Pilasters
Counterforts
differential movements between load positions
Helical Ties
Geofoam
Dynamic Compaction
Mat and Raft Foundations (2)
Caissons (1)
• Used when following conditions are present:
▫ Structural loads too high ▫ Not uniformly distributed lateral loads ▫ Soil conditions poor ▫ Uplift loads are large ▫ Groundwater table located below structure • Rule of Thumb: ▫ Spread footings covers more than 50% of building footprint
• Prefabricated hollow box or cylinder • Transferred into the ground and filled with concrete • Drilled into bedrock or deep underlying strata
Caissons (2)
Monolithic
• Poured as one structure • Frost protected • Relies on two sheets of rigid insulation ▫ One placed outside of foundation wall ▫ One laid flat on bed of gravel • Prevents freezing • Insulation holds heat
• Often used when structures require foundation beneath rivers or other bodies of water • Caissons can be floated to job site and suck into desired location • Similar in form of a pile but installation varies
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