TECHNICAL
Enter the Geopier
Rammed Aggregate Pier®
The Geopier RAP system for ground improvement
Ground improvement techniques have become more
widely used in Canada over the past decade and owners,
developers, contractors and engineers have gradually
taken notice of the unique advantages offered by
using ground improvement techniques. Of the many ground
improvement techniques used in Canada, few have been employed
more often than the Geopier Rammed Aggregate Pier®
(RAP) system. Since 2006, many thousands of linear kilometres
of Geopier RAP elements have been installed in Canada
to support industrial, commercial and residential projects,
and other applications such as liquefaction mitigation, embankment
and wall support, and other structures. Since its
introduction in the U.S. over 30 years ago, the Geopier RAP
system reinforces a wide variety of soil types including undocumented
fill, loose sands, soft/sensitive clays, silts and
trapped organics to provide increased bearing capacity and
engineered settlement control.
RAP systems have been used worldwide since the early
1990s. “Stone columns,” now branded as “aggregate piers” or
“vibro stone columns,” were first developed in Germany to
densify loose sand soils using a horizontally vibrating probe
with surface fed aggregate.
The precision RAP system called Geopier® was developed
by the Geopier Foundation Company to provide an efficient
intermediate foundation solution for the support of settlement
sensitive structures in more difficult soil conditions.
These systems were originally developed as an alternative
to excavation and replacement in more cohesive soils. Due
to its unique construction method, Geopier RAP elements
provide greater capacity than stone columns – particularly
in non-sand soil conditions (clay, silt, organic containing and
fill soils).
Both Geopier RAP elements and traditional stone columns
are constructed with stone. However, traditional stone
columns are installed using suspended vibratory probes that
only deliver horizontal vibration, while Geopier RAP elements
are constructed using the patented Geopier bevelled
tamper to deliver a high magnitude of vertical compaction
energy and 15 to 30 tonnes of direct crown pressure during
the vertical compaction of each lift; which results in a stiffer
By Mark Tigchelaar, P. Eng., GeoSolv Design/Build
PHOTOS AND ILLUSTRATIONS: GEOSOLV DESIGN/BUILD
PILING CANADA 55