CEMP-E
TI 809-02
1 September 1999
3-6. DEEP FOUNDATIONS. Deep foundations such as piles or pier foundations are needed
to transmit the load of a building through a material of poor bearing capacity, or to eliminate
differential settlements. The choice of pile or pier type for a given foundation should be made
on the basis of a comparative study of cost, permanency, stability under vertical and horizontal
loading, and the required method of installation. Additional information on pile and pier
foundations can be found in the publications listed in Appendix A.
a. Pile Foundations. Pile foundations can consist of concrete, wood, or steel elements
either driven or drilled into the ground. Piles are relatively slender in comparison to their
length. Piles derive their load carrying capacity through skin friction, end bearing, or a
combination of both. Two of the pile types common to building construction, along with their
advantages and disadvantages, are described below. Design of pile foundations will comply
with the provisions of EM 1110-2-2906, "Design of Pile Foundations," or Navy Design Manual
(DM) 7.02, "Foundations and Earth Structures," and Military Handbook (MIL-HDBK) 1007/3,
"Soil Dynamics and Special Design Aspects."
(1) Steel H-Piles. Steel H-piles are rolled steel sections with wide flanges so the depth
of the section and widths of the flanges are about equal dimension. The cross-sectional area
and volume of the H-pile are relatively small; consequently, they can be driven through
compacted granular materials and into soft rock. Steel H-piles because of their small volume
displacement have little or no effect in causing ground swelling or rising of adjacent piles.
Steel piles protruding above the ground lines are subject to corrosion at or somewhat below
the ground line. Steel piles are ductile and therefore are suitable for use in high seismic areas.
(2) Prestressed Concrete Piles. Prestressed concrete piles are used and have
replaced for the most part the reinforced concrete precast pile. Some of its advantages are
prestressing eliminates open cracks in a concrete pile, permits ease in handling, and reduces
the tendency to spall during driving. The compression induced in the pile permits piles to
sustain considerable bending stresses. However when used in high seismic areas, prestressed
concrete piles must contain large quantities of confinement steel in the form of spiral
reinforcement to resist the curvature demands place on the pile by differential subsurface
ground distortions. The transverse confinement reinforcement is similar to that required for
reinforced concrete columns in high seismic areas (Site Class D, E, or F per TI 809-04).
Information on the amounts of transverse reinforcement required for various regions of the pile
can be found in two PCI Journal Papers: "Seismic Design of Prestressed Concrete Piling" PCI
JOURNAL, V.28, No. 2, March-April 1983, and "Simulated Seismic Load Tests on Prestressed
Concrete Piles and Pile-Pile Cap Connections," PCI JOURNAL, V.35, No. 6, November-
December 1990. The later PCI Journal Paper also provides valuable information on pile to pile
cap connections.
b. Pier Foundations. Pier foundations are constructed by digging, drilling, or otherwise
excavating a hole in the soil, which is subsequently filled with plain or reinforced concrete.
Steel casings may or may not be used to facilitate pier construction. Two pier foundation types
common to building construction, along with their advantages and disadvantages, are
described below. The design of pier foundations will follow the recommendations contained in
ACI Committee Report 336, "Suggested Design and Construction Procedures for Pier
Foundations."
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