September/October 2022 - 87

FEATURE ARTICLE
Self-Drilling Micropiles
The Santa Fe train station and passenger
rail platform were constructed in the
downtown district of Fort Madison,
Iowa, over a century ago. This landmark
building and rail platform were in need
of major renovations and rehabilitation
in order to restore the site to a
functioning railway train station. A
multitude of key players from various
public and private parties were involved
in the design and construction of this
project site.
Part of the project consisted of
constructing the passenger platform.
The original design included helical
piles to provide foundational support for
the platform. Challenges occurred
during construction due to the presence
of an obstruction in the form of a poured
concrete slab in the immediate area
where the helical piles were to be
installed. The contractor worked with
the engineer of record and other
consulting parties to value engineer the
helical pile design and utilize selfdrilling
micropiles as a replacement to
the specified helical pile system.
Hollow Bar Option
The contractor utilized a threaded
hollow bar micropile system. The
hollow bar simultaneously acts as the
AUTHORS Matt Sotirin, P.E., and Marc Mastrantuono, P.E., Ischebeck USA
DEEP FOUNDATIONS * SEPT/OCT 2022 * 87
drilling rod, grout injection tube and
structural reinforcement for the
micropile. These systems can be used
in most soil types, including unstable
soils, without the need for temporary
casing. With the use of a sacrificial drill
bit, the hollow bar is drilled, with
additional bars being added using
couplers, until the desired micropile
depth is reached. A structural cement
grout is then injected through the
hollow bar that produces a grout body
that encapsulates the structural
reinforcement (hollow bar) and bonds
with the surrounding soil. The pumping
of the grout also further improves the

September/October 2022

Table of Contents for the Digital Edition of September/October 2022

TOC
September/October 2022 - Intro
September/October 2022 - 1
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September/October 2022 - TOC
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