CEMP-E
EI 02G001
01 July 1997
4-2. PILE INSTALLATION. Installation of the production piles, those piles that are intended to support the
structure under construction, will be monitored and records kept to provide data to assess the capacity and
quality of the pile foundation.
a. Pile Driving Records. A complete pile driving record will be prepared for each pile driven to its
embedment depth. These records provide important data concerning the nature of the soils that are
penetrated, provide evidence of any soil disturbance that is a result of driving, and indicate the penetration
resistance. The penetration resistance, pile driving analyzer data recorded during driving of indicator and
some of the production piles, and recorded later during restrikes, can be analyzed to assess the driving
stresses, capacity, and quality of the pile.
(1) Impact Hammers. The make, model, energy, stroke, pile, and hammer cushions should all
be recorded on the header portion of the record. The remaining portion of the pile driving record is used to
record the penetration resistance (blows applied to the pile within a unit distance such as 1 foot.
(a) A wave equation analysis should be performed if blow counts that are recorded are not
similar to those observed during driving and restrike of the indicator piles at the start or prior to construction.
(b) The blow counts should be plotted as a function of depth to determine depths where the
soil may be strongest and to indicate if the pile had been driven to the proper embedment depth and
bearing stratum.
(c) The average blow count should be computed for each pile and the average of each pile
plotted versus time. This plot will indicate if the penetration resistance is changing as additional piles are
installed. Increases in the penetration resistance with time may indicate that the soil is getting stronger,
perhaps from densification of the soil as a result of driving. Increasing penetration resistance with time may
also indicate a temporary drop in pore water pressure as a result of the disturbance of dense sands or stiff
clays. Decreases in the penetration resistance with time may indicate driving into weaker soil or perhaps
the temporary buildup of excess pore pressures if the soils are loose and fine grained with low permeability.
(d) Abrupt changes in penetration resistance will be investigated to determine the cause.
Abrupt changes can indicate a variety of problems that will cause the pile to be rejected. The pile should be
replaced if driving damaged the pile. The installation equipment may have to be changed to install a
different type of pile and pile length.
(2) Vibratory Drivers. The make, model, weight, dynamic force, frequency or range of
frequencies, maximum eccentric moment, and clamping method will be recorded on the form. The
remaining portion of the form will be used to record the depth, the time to reach a given depth, and the
frequency to reach the depth.
(a) The ultimate piling capacity cannot yet be determined from vibratory driver records. An impact
hammer is required to drive the pile to the embedment depth.
(b) A static load test is typically required to verify that vibratory driven piles have adequate pile
capacity. Specifications should require a static load test for each type of pile and soil.
(c) Steel H-piles and pipe piles can be easily clamped to a vibratory driver. Concrete and timber
piles may require bolts to secure the vibratory driver.
(d) The vibratory driver is nearly always the most efficient tool for extracting a pile and should be
used for steel, wood, or concrete. The vibratory driver first breaks the pile loose from the soil and then extracts
the pile. A line attached directly to the pile can aid extraction when the pile is too heavy for the driver.
4-5
Previous Page
