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p 229
Chapter 3
Hydraulically-Driven Push Piers
CHAPTER 3
HYDRAULICALLY-DRIVEN PUSH PIERS
3.5 Benefits
Some of the benefits of hydraulically-driven steel
push pier systems versus other underpinning
systems may include:
• Pre-manufactured components increase the
quality control of the installed system
• Components available with zinc coating for
additional corrosion resistance
• Laboratory testing of the push pier system and
components documents the system capacity
• Eccentricity between the shaft and bearing
area is minimized to reduce the bending
moment transferred to the pier system,
allowing superior performance when stabilizing
or lifting the structure
• Drive and lock-off forces easily determined
using hydraulic pumps and cylinders
• Documentation of the final drive force and
lock-off force is used to verify a factor of safety
at each pier location
• A proof load test is essentially completed for
each pier installation
• End bearing pier is driven deep through
problem soils
• Additional skin friction develops after
installation increasing the factor of safety
against pier settlement
• Steel reinforcement and grout added within
hollow pier sections improves lateral capacity
and pier stiffness
• Installs with portable hydraulic equipment
• Can be installed within areas of limited or
difficult access
• Can be installed in areas of low overhead
clearance (crawl spaces)
• Easy to install
• No vibration
• Installs quickly from inside or outside the structure
• Cost-effective solution
3.6 Limitations
The use of push pier systems is limited to
structures that have sufficient structural
load and/or contributory soil load to provide
adequate resistance to advance the piers to a
competent bearing stratum. Push pier systems
are generally considered for compression-only
applications and are not considered for lateral
capacity. Foundation Supportworks published
system capacities are based on the following
assumptions:
• The systems should be used on structures
that are fixed from translation or braced in
some manner to prevent translation of the
foundation.
• Concrete bearing assumes a minimum
compressive strength (f’c) of 2,500 psi. Local
concrete bending and other local design
checks should be evaluated on a case by case
basis.
• The surrounding soils provide continuous
lateral support with SPT N-values greater
than or equal to 4 blows per foot. Piers with
exposed unbraced lengths or piers placed in
weaker or fluid soils should be evaluated on a
case by case basis.
• The maximum recommended drive load is not
exceeded during installation.