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Chapter 3
Hydraulically-Driven Push Piers
CHAPTER 3
HYDRAULICALLY-DRIVEN PUSH PIERS
3.7 Corrosion Protection
Foundation Supportworks’ hydraulically-driven
steel push pier systems have been designed
following the guidelines of ICC-ES AC358 and
ICC-ES AC406 for corrosion loss rates and
design period (50 years).
The starter and pier tube sections used for
Models PP288 and PP350 push pier systems
are manufactured with a triple-layer, in-line
galvanized coating. The triple-layer coating
process consists of a uniform galvanized zinc
coating, an intermediate conversion coating to
inhibit the formation of white rust and enhance
corrosion resistance, and a clear organic
polymer top coating which interacts with the
intermediate coating to further enhance the
corrosion protection and durability. The insides of
the PP288 and PP350 starter and pier tubes also
have a zinc-rich coating. Although the triple-layer
coating offers significant corrosion resistance,
the process is not specifically recognized within
AC358 and AC406. The PP288 and PP350 push
pier system capacities provided in Appendix 3A
are therefore conservatively based on corrosion
losses for plain steel.
The starter and pier tube sections for the PP237
and PP400 push pier systems are available in either
plain steel or with a hot-dip galvanized coating in
accordance with ASTM A123. The FSI push pier
system brackets, external sleeves, and pier caps
are also available as either plain steel or hot-dip
galvanized (ASTM A123). The bracket hardware is
electro-plated in accordance with ASTM B633.
Additional corrosion protection may be achieved
by filling the pier tubes with a fluid grout or concrete
mix following installation. With a dry hole and using
a neat or sand mix, the grout may be gravity fed
from the top of the pier. In a wet hole, to prevent
segregation of aggregate, or to prevent bridging
effects, the grout may be placed by tremie tube
from the bottom of the pier toward the surface.
Pier tubes can also be filled with concrete or grout
at intervals during the installation; i.e., piers are
gravity filled from the top after advancement of
every one or two sections.
3.8 Push Pier
Installation Equipment
The equipment needed to first drive the piers
individually and then transfer the structural load
to the multiple pier locations consists of hydraulic
cylinders, a hydraulic pump, a remote valve
assembly (or other control device), hoses and
fittings, drive stands and lift cylinder assemblies.
Safety precautionsmust be followedwhenusing
high pressure hydraulics. The pressure rating
of each system component must be verified
prior to use to ensure that all components
meet the maximum pressure rating required
during the installation. Hoses and fittings
should be checked periodically for damage and
replaced when in question. Failure to follow
manufacturer’s specifications may result in
equipment failure and/or personal injury.