FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

10 DESIGNING THE FOUNDATION Volume II
10.5.4 Pile Installation
Methods for installing piles include driving, augering, and jetting. A combination of methods may also be
used. For example, piles may be placed in augered holes and then driven to their final depth. Combining
installation methods can increase the achievable embedment depth. With increased depths, a pile’s resistance
to lateral and vertical loads can be increased, and its vulnerability to scour and erosion will be reduced.
Driving involves hitting the top of the pile with a pile driver or hammer until the pile reaches the
desired depth or it is driven to refusal. Piles can be driven with vibratory hammers. Vibratory hammers
generate vertical oscillating movements that reduce the soil stress against the pile and which makes the
piles easier to drive. Ultimate load resistance is achieved by a combination of end bearing of the pile and
frictional resistance between the pile and the soil. A record of the blow counts from the pile driver can
be used with a number of empirical equations to determine capacity.
Augering involves placing the pile into a pre-drilled hole typically made with an auger. The augured
hole can be the full diameter of the pile or a smaller diameter than the pile. Pre-drilling is completed to
a predetermined depth, which often is adjusted for the soils found on the site. After placing the pile into
the pre-drilled hole, the pile is then driven to its final desired depth or until it reaches refusal.
Jetting is similar to augering but instead of using a soils auger, jetting involves using a jet of water (or
air) to remove soils beneath and around the pile. Like augering, jetting is used in conjunction with pile
driving.
Both augering and jetting remove natural, undisturbed soil along the side of the pile. Load resistance for
both of these methods is achieved by a combination of end bearing and frictional resistance, although the
frictional resistance is much less than that provided by driven piles.
Figure 10-5 illustrates the three pile installation methods. Table 10-9 lists advantages and special considerations
for each method.
Figure 10‑5.
Pier installation methods
10-20 COASTAL CONSTRUCTION MANUAL