01 July 1997
encountering changed conditions. Avoidance of such a situation requires professional judgment and
customer education. A waiver requirement by higher authority to the pile testing procedures for verifying
design is described in chapter 6 of TM 5-809-7.
(b) Data from the exploration program should be made available to designers and prospective
bidders and contractors and should include complete boring logs showing all encountered strata, locations
of changes in strata, and locations of groundwater including perched and artesian pressures.
(c) Cobbles and boulders should be indicated because they may interfere with the driving of
(d) Landfills often contain poorly compacted materials and may not provide soils that will
provide adequate pile capacity.
(e) The soil actually encountered during installation of the piles may not provide the
penetration resistance that was expected from results of the soil exploration program. A variety of problems
can be encountered leading to unexpected behavior of the driven pile as discussed in paragraph 4-3. Costly
delays from unexpected pile behavior can be minimized by driving indicator piles with PDA equipment and by
performing load tests as discussed in paragraphs 2-2b, 2-2c, and 2-2d below.
(f) Refer to TM 5-818-1 and TM 5-809-7 for guidance on the exploration program.
(2) Economy of Piles. The most economical piles will usually be those that can be obtained and
(a) Cost estimates should be prepared and a comparison made of alternative pile materials
and construction methods.
(b) The least cost alternative capable of providing acceptable pile capacity should be selected
depending on the skills of the local construction force, availability of materials, and availability of equipment
to install the piles.
(c) Alternative piles where costs are within 15 percent of each other should be included in the
b. Indicator Piles. Indicator piles are the same as the actual production piles used to support the
structure. These piles are driven at the start of construction to provide information on the behavior of the
piles during their installation and to provide an assessment of the actual capacity of the piles. Indicator piles
are usually designed to be part of the production piles that support the structure.
(1) Driving of Indicator Piles. Depending on the job size of the production piles, 2 to 5 percent is
typically driven as indicator piles at locations specified by the design engineer or at locations that may have
inadequate pile capacity.
(a) Locations where indicator piles should be driven include the corners, edges, and center of
the site where piles are to be installed.
(b) Indicator piles should be driven at locations where the soil exploration program indicated
relatively low standard penetration resistances, loose sands, or soft clays.
(c) The driving of indicator piles in loose sands or some clay soils may indicate penetration
resistances that are too low to provide adequate pile capacity. Driving the piles may also cause pore water
pressures to increase and further reduce the penetration resistance. Dissipation of pore water pressures
over time will cause the penetration resistance to increase and lead to a pile with greater capacity. This is