Geopier gave a presentation at the GI/CEC Continuing Education Event in March 2015

1. Ground Improvements for Challenging Sites in
Orange County
Compacted Aggregate Piers
(Geopier/Rammed Aggregate Pier)

2. Outline
1. Compacted aggregate pier basics
2. Two Case Studies
• The Park Apartments
• Park Place Apartments
3. Construction QA/QC
4. Questions and Discussion

3. Generic:
• compacted aggregate pier
• compacted aggregate caisson
• compacted aggregate column

4. Basic Concept

5. Proprietary (Trade Names):
• Geopier - Rammed Aggregate Pier
• TerraRam
• GeoRam
• VibroPier
• Earth Pier
• Etcetera Etcetera Pier

6. Geopier drill
Geopier Tamper
Skid steer
 Mobile crew (4 people, 3 machines)
 Rapid installations (30 – 50 per day)
 Safe, clean, dry process (no jetting!)
 Installation depths up to 30 feet
Geopier GP3™ Construction

9. Engineering Aspects
• Not a foundation system
• Improve near surface soil
• Increased bearing capacities below
foundations and slabs-on-grade
• Reduced settlements

10. Settlement Within Compacted Aggregate Zone
Design based on spring analogy:
 Rigid footing: Geopier deflection & matrix soil deflection
 Stiff spring (RAP element) takes more load than soft spring (matrix
soil).

11.  Use conventional geotechnical analysis
approaches:
 Estimate footing-induced stress
(Westergaard, Boussinesq, etc)
 Estimate soil compressibility
 Traditional elastic or consolidation
design methods.
 Add lower zone and upper zone for
total settlement
Settlement Below Aggregate Piers (Lower Zone)
B
2B
HLZ
HUZ

12. Design Process
• Foundation Loads
• Settlement tolerances
• Onsite soil properties
• Collaboration
– Geotechnical consultant
– Structural engineer
– Aggregate pier designer/builder

15. Two Project Applications
1.The Park
2.Park Place

16. The Park Apartments

17. The Park Project
• 1500 apartment units on 29-acres
• 4-story wood framed apartment buildings
over 2 levels of partial subterranean parking
(podium)
• Column loads 380 to 1156 KIPS

18. The Park---site conditions
• Relatively flat site
• Historically used for agriculture
• Explored with hollow-stem borings and CPT’s
• Groundwater wells.
• Underlain by deep alluvium
• Interlayered silts, sands, clays
• Groundwater at 15 to 30 feet BGS

19. Geotechnical Issues
• Groundwater below subterranean levels
(5 to 10 feet)
• Reduced bearing capacities
• Differential foundation loads and
differential settlements

20. Alternatives
× Piles infeasible
× Remedial Grading---groundwater
× Matt foundation ($7 million)
Ground improvement---aggregate piers

21. Geopiers at The Park
• 2,400 piers
• 30-inch diameter
• 11 to 13 feet deep
• 50 to 60 working days
• Savings over mat foundation: $3 million

22. Acknowledgements
Project Owner: Irvine Company
Specialty Contractor: Geopier
Structural Engineer: Van Dorp Chow

23. Park Place Apartments

24. Park
Place
San Diego Creek

25. Park Place Project
• 980 units on 14-acres
• 4-story wood framed buildings
• 2-levels, partially subterranean,
reinforced concrete parking below
• Column loads: 94 to 807 kips
• Wall loads: <12.5 kips/l.f.

26. Park Place --Site Conditions
• Relatively flat site
• Formerly MARSHLAND (swamps)
• Underlain by PEAT/organic clays, alluvium
• Groundwater at 20 to 30 feet BGS

27. MARSH DEPOSITS
Older Alluvium
Groundwater
Structure
Younger Alluvium

28. Geotechnical Issues
• Very low bearing capacities
• 4 inches total settlement in alluvium (2 inches
differential)
• Mat foundations infeasible over marsh soils
• Conventional aggregate piers inadequate in
marsh deposits (peat)

29. Geopiers at Park Place
• 4,798 piers
• 24-inch diameter
• 9 to 13 feet deep
• Cement Treated Piers (474)
in MARSH Deposit areas
• Cement Treated Piers---up to 30’ deep

31. Acknowledgements
Project Owner: Irvine Company
Specialty Contractor: Tensar-Geopier (Western Ground
Improvement)
Structural Engineer: HCDA Engineering, Inc.

32. Construction QA/QC
• Aggregate
properties
• Surface logging of
excavated soil
• Pier depths
• Pier locations

34. Purpose: Measure Stiffness (kg)
W-Beam
Uplift
Anchor
Rod
100 Ton Jack
Uplift
Anchor
PierTelltaleCompression Pier
Insitu Modulus Test

35. Discussion/Questions