Aggregate Piers
Aggregate piers are compacted stone columns  used to reinforce silt, clay and variable fill material. Aggregate piers are constructed by predrilling an open hole to the treatment depth, backfilling with rock and compacting it in lifts with a specialty Vibro-Probe or compaction equipment.  In soil profiles where the predrilled hole may collapse, bottom feed equipment can be used to place rock.


  • Aggregate piers are installed in non-granular soil profiles generally with a deeper ground water table
  • Low to mid rise new construction buildings
  • Area loads such as tanks and embankments
  • Liquefaction mitigation

Construction Advantages

  • Very economical compared to to deep foundation systems
  • Increased allowable soil bearing capacity reduces the size of foundations
  • Expedient process and minimal site disturbance

What to Expect

  • Earth Tech will provide a signed and sealed design indicating the treatment plan
  • Site clearing and access preparation precede the Aggregate Piers
  • Large quantities of rock backfill are required, thus site access for rock truck deliveries is needed
  • Typically, this work is performed under a performance specification, with minimum criteria regarding bearing capacity and settlement. Load tests are used to verify results.
  • Final site grading, spoils clean up and foundation construction follow Aggregate Pier installation
  • Drilling spoils may accumulate on the surface and disposed of on or off site