01 July 1997
quality assurance record.
4-4. COMPLICATIONS. Driving of the production piles may lead to complications that could compromise
the capacity of the foundation and interfere with the operation of adjacent structures. These complications
can be caused by penetration resistances that are either too low or too high when driven to the embedment
depth, by ground movement, and by environmental problems. Refer to paragraph 4-3 for solution to
problems with pile integrity.
a. Problems with Low Resistance. The pile foundation will not have sufficient capacity if the
penetration resistances are too low. Abrupt unexpected reductions in the penetration resistance may
indicate a damage pile. Guidance for the solution of this problem is considered in paragraph 4-3. Other
causes of low penetration resistance include soil freeze, soils with low strength, and driving into a landfill.
Materials in landfills will usually be poorly compacted.
(1) Driving of Initial Piles. If the first production piles driven in a group have penetration
resistances that are too low, then one must first check to be sure that the hammer and driving energy are
adequate and similar to those used for driving near indicator piles prior to or at the start of construction.
PDA data must be obtained if the equipment is available, and driving stresses, capacity, and pile quality
must be checked. PDA equipment should be available during the driving of the first piles and used to assist
(a) If pile capacity is not adequate at the embedment depth as indicated by low penetration
resistance or the PDA, but the pile is not damaged and driving stresses are satisfactory, several additional
piles may be driven as specified in the contract documents. The first piles driven in a group often have
penetration resistances that are lower than those driven later. Driving tends to compact the soil and to
increase the penetration resistance.
(b) Plot the average penetration resistances of the piles that were driven as a function of time
to see if the penetration resistances had increased with time and have reached a satisfactory level. The first
piles that were driven in a group should be restruck after driving additional piles to see if the penetration
resistances and pile capacity have increased to a satisfactory level.
(c) If the penetration resistances and pile capacity have not increased to an adequate level,
then other options should be considered. Such options are driving the piles to a deeper embedment depth,
driving additional piles to reduce the spacing between the piles and increase the number of piles in the
group, or use a vibratory driver to compact the soil. A cost and efficiency comparison should be made
between these options, and the most cost effective option should be selected first.
(2) Piles Driven Later. If piles driven later in a group do not have sufficient penetration resistance,
then the cause may be from the effects of soil freeze, from weak soils such as loose sands or soft clays, or
from subsurface voids.
(a) If the penetration resistance of the pile remains low when driven, the pile should be
restruck after a 1-, 2-, or 5-day delay to determine if soil freeze effects are present. The penetration
resistance of restruck piles should be plotted as a function of time to determine the rate of increase in
penetration resistance. Adequate capacity may develop after a sufficient delay following pile installation.
Soils subject to freeze include loose to medium dense sands, silts, and clays.
(b) If the penetration resistance is low, although driving energy is adequate, there is no
evidence of pile damage. If restrike does not provide larger blow counts, then the soils may be weaker than
anticipated from results of the exploration program. Driving of additional piles or driving to a deeper