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Rammed
Aggregate Pier® Systems
General
Q: For which types of projects have Rammed Aggregate Pier®*
(RAP) Systems been used?
A: RAP Systems have been used to support hundreds of projects in
over 40 states and 8 countries. RAP solutions are used to support
commercial, residential, industrial and transportation applications
including buildings up to 20 stories tall, industrial tanks, heavily
to lightly loaded floor slabs, MSE walls and embankments and other
transportation structures. RAP Systems are also used to provide
liquefaction mitigation, uplift resistance and increased resistance
to lateral loads.
Q: Who designs Rammed Aggregate Pier®* Systems?
A: Regional
Engineers with Geopier Foundation Company detail RAP Systems using
loads provided by the project structural engineer and geotechnical
information provided by the geotechnical engineer. Professional
engineers, registered in the state where the project will be constructed,
develop the design. After preliminary design work is completed,
every project undergoes an internal peer review process by engineers
in the main office. Before going to construction, “shop”
drawings are prepared and stamped by a P.E. and provided to the
general contractor.
Q: Who installs Rammed Aggregate Pier®* Systems?
A: Geopier
Australia install RAP Systems. We provide a design-build service
to the general contractor and installs the RAP System per the drawings
and specifications.
Q: How does the project team interact with Geopier Australia?
A: The Design
Engineer from Geopier Australia works closely with all members of
the project team including the geotechnical and structural engineer,
architect, developer, civil engineer and general contractor. Using
the geotechnical information provided by the geotechnical engineer,
the Geopier Design Engineer develops RAP solutions for the project.
The specific design solution is formulated by using the structural
loading conditions and drawings provided by the structural engineer
or architect. Working with the licensee to create a seamless transition,
the Design Engineer provides a lump sum bid for the RAP System design
to the general contractor. The Design Engineer and installation
team works closely with the general contractor to coordinate construction
and meet project-specific schedule deadlines.
Q: Does Geopier Foundation Company provide errors and omissions
insurance?
A:Geopier Foundation
Company provides errors and omissions insurance upon request for
projects. Our errors and omissions insurance includes a $2 million
dollar per occurrence and $3 million dollar aggregate policy.
Technical
Q: What are Rammed Aggregate Pier® Systems?
A: An Intermediate
Foundation®* system engineered, designed and installed exclusively
by representatives of Geopier Foundation Company. RAP Systems are
constructed by densely compacting successive thin lifts of high
quality crushed rock in a 400 to 800mm cavity of varying depth using
patented ramming equipment. The vertical ramming action increases
the lateral stress and improves the soils surrounding the cavity,
which results in foundation settlement control and greater bearing
pressures for design.
Q: How do Rammed Aggregate Pier®* Systems work?
A: The combination
of the installation of the stiff aggregate columns and significant
lateral stress increase in the matrix soil beneath the footing raises
the allowable bearing pressure on the order of 2 to 3 times the
unreinforced allowable bearing pressure and controls settlement
to the project design criteria. RAP elements are installed individually
or in groups to support shallow foundations or floor slabs. This
often eliminates the need for deep foundations and structural floor
slabs.
For applications
where shear resistance is the controlling design factor (for example,
global stability of retaining walls or embankments; and stabilization
of landslides), RAP Systems are installed to increase the composite
shear resistance. With measured friction angles of the constructed
element ranging between 49 and 52 degrees, RAP elements provide
significant increases in shear resistance and afford increases in
the factors of safety for stability. For more information, please
download or request Technical
Bulletin No. 5 on RAP Systems, shear resistance for global stability
and slope stability.
Q: What types of soil conditions are appropriate for Rammed Aggregate
Pier®* Systems?
A: RAP Systems
are incredibly versatile because they can be installed using either
a displacement or replacement method; therefore RAP Systems are
effective in reinforcing good to poor soils, including soft to stiff
clay and silt, organic silt and peat, loose to dense sand, mixed
soil layers, uncontrolled fill and soils below the ground water
table.
Q: Do the Rammed Aggregate Pier®* elements need to extend
to a dense soil layer or rock?
A: RAP elements
do not need to extend to a firm bearing layer like a pile foundation.
The Systems are designed to improve the existing soil with the inclusion
of dense aggregate columns and reinforce the soil within a zone
beneath shallow footings where the stresses are the highest. In
order to accomplish this, RAP elements are typically installed to
depths ranging between one and two times the foundation width for
settlement control.
Q: What are typical installation rates for Rammed Aggregate Pier®*
Systems?
A: Rates depend
on factors including drill depths, aggregate haul distances and
site conditions. Often, installation rates range from 30 to 50 RAP
elements per day.
Q: How do Rammed Aggregate Pier®* Systems work in seismic
environments?
A: Download
or request Technical
Bulletin No. 1 on performance of RAP supported footings under
seismic loading conditions.
Q: How do Rammed Aggregate Pier®* Systems resist lateral
loads?
A: RAP Systems
resist lateral loads through mechanisms similar to shallow foundations.
For more information, download or request Technical
Bulletin No. 4 on lateral resistance.
Q: How do Rammed Aggregate Pier®* Systems resist uplift loads?
A: RAP Systems
resist uplift loads through resistance that develops along the perimeter
of the RAP element as an uplift anchor located at the bottom of
the RAP is pulled upward. For more information, download or request
Technical
Bulletin No. 3 on uplift resistance.
*Rammed Aggregate Pier and Intermediate Foundation
are registered trade marks in the USA of Geopier Foundation Company
Inc.
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