Aggregate Piers

When a structure is to be built on soils not suitable for shallow foundations, aggregate piers are often an economical alternative to other options such as undercut and replace or a deep foundation system.

  • Reduces settlement and increases the bearing capacity of in-situ soils
  • Reduces cost and time uncertainties during the pre-construction phase associated with undercut and replace
  • Simplifies foundation concrete work by using shallow foundations rather than pile caps
  • Sites containing deep undocumented fill
  • Sites with deep compressible soft soils   
  • Heavy building loads that require excessively large footings if supported by in-situ soils
  • There are 2 methods of aggregate pier construction:
    • Top Feed – Soil conditions conducive to open hole drilling methods
    • Bottom Feed – Soil conditions where the soil is not expected to stand up for a suitable period of time
  • Top Feed Installation Process:
    • Pre-drill the aggregate pier location the full design depth
    • Lower the Vibroflot to the bottom of the pre-drilled hole
    • Dump stone from the top into the hole
    • Build the aggregate pier in successive lifts up to the ground surface
  • Bottom Feed Installation Process:
    • Advance the Vibroflot into the ground to the design aggregate pier depth
    • Pour stone into a hopper mounted at the top of the Vibroflot
    • The stone from the hopper travels down a tube that discharges at the tip of the Vibroflot
    • Build the aggregate pier in successive lifts up to the ground surface