01 Jul 97
and/or adhesion mobilized between the surface concrete and
stiffness used in design. The cyclic reduction factor used in
the surrounding soil.
design can be verified if the test pile is loaded for
approximately 100 cycles. Some aspects of the lateral load
(c) The dial gauges are usually attached to a reference
beam supported by two posts driven into the ground a
sufficient distance apart (i.e., 10 feet or two shaft diameters,
(1) Monotonic and cyclic lateral load tests should be
whichever is larger) (Figure 6-4) to eliminate the influence
conducted and recorded according to ASTM D 3966. Tests
of shaft movement during the test. The difference in
should be conducted as close to the proposed structure as
reading between dial gauge 1 and dial gauge 2 at any
possible and in similar soil.
pressure level represents the elastic compression of the
concrete. The load downward-deflection curve in end
(2) Lateral load tests may be conducted by jacking one
bearing and the load upward- movement curve in skin
pile against another, thus testing two adjacent piles. Loads
friction can be plotted from the test data to determine the
should be carried to failure.
ultimate load of the drilled shaft. Failure may occur in end
(3) Groundwater will influence the lateral load response
bearing or skin friction. At that point the test is considered
of the pile and should be the same as that which will exist
complete. Osterberg cells can be constructed as large as 4
during the life of the structure.
feet in diameter to carry a load equivalent to 6,000 tons of
(4) The sequence of applying loads is important if
cyclic tests are conducted in combination with a monotonic
(6) Analysis of capacity. Table 6-4 illustrates four
lateral load test. This may be done by first selecting the
methods of estimating ultimate capacity of a pile tested to
load level of the cyclic test using either load or deflection
failure. Three methods should be used when possible,
guidelines. The load level for the cyclic test may be the
depending on local experience and preference, to determine
design load. A deflection criterion may consist of loading
a suitable range of probable ultimate capacity. The
the piles to a predetermined deflection and then using that
methods given in Table 6-4 give a range of Qu from 320 to
load level for the cyclic load test. Using the cyclic load
467 kips for the same test data.
level, the test piles would be cyclically loaded from zero
loading to the load level of the cyclic load test. This
(7) Effects of layered soils. Layered soils may cause the
procedure should be repeated for the required number of
test piles to have a different capacity than the service piles
cycles. Dial gauge readings of lateral deflection of the pile
if the test piles have tips in a different stratum.
head should be made at a minimum at each zero load level
and at each maximum cyclic load level. The test pile
may also cause the load to be supported by another layer.
should be loaded laterally to failure after the last loading
The support of a pile could change from friction to end
The last loading cycle to failure can be
bearing or the reverse depending on the strata.
superimposed on the initial loading cycle to determine the
lateral load-deflection curve of the pile to failure.
e. Lateral load test. This test is used to verify the