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Geotechnical engineering principles are used in the
design of the Geopier® system.
The Geopier-reinforced zone (referred to as the Upper Zone in settlement
analyses) extends to a depth equal to the Rammed Aggregate Pier® shaft length plus
one pier diameter. The addition of one pier diameter accounts for
prestressing that is developed at the base of the pier shaft during
bottom stabilization.
Deformation in the Geopier-reinforced zone occurs as vertical load
is applied at the base of the footing, mat, slab, or embankment.
Applied stresses concentrate in the Rammed Aggregate Pier® in proportion
to the relative difference in stiffness between the piers and the
intermediate matrix soils. Due to the high stresses
transferred into the piers, the upper portion of each pier bulges
slightly, which further increases lateral stress in the matrix soil
and adds to the stiffness of the Geopier-reinforced zone.
Ideally
when the foundation system is loaded, deformation occurring at the
bottoms of the Rammed Aggregate Pier® shafts is so small that the load can be assumed
to be fully transferred into the Geopier-stiffened Upper Zone. Foundation
settlement attributable to Upper Zone deformation is calculated
by detailed, conventional analysis.
Foundation settlement resulting from stresses which
might reach the soils beneath the Geopier-reinforced zone (the Lower
Zone) can be estimated by means of various accepted geotechnical
analysis theories. Because some analysis theories are more appropriate
for plastic soils, and others are more applicable to sands and non-plastic
silts, the selection of the most appropriate theory(ies) is very
important.
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