D 1143 covers procedures for testing vertical or inclined deep foundations individually or in groups to determine the axial deflection in response to a static axial compressive load. Subcommittee D18.11 has recently approved an extensive revision of D 1143 that reflects the latest technology used for these purposes.
“The test apparatus used in this practice has improved significantly in accuracy and capability, but D 1143 had not reflected this,” says Paul
Bullock, Ph.D., senior engineer, GRL Engineers, and D18.11 chair. “Deep foundation elements have also gotten bigger and may now support loads in excess of 1,000 tons for larger structures. So the standard of care needed to obtain good test results for design purposes has also been elevated. The previous version probably contemplated maximum loads in the range of 500 tons. Also, we needed to maintain backward compatibility with these lightly loaded foundations that likely still comprise the bulk of the tests performed.”
Bullock notes that the new version of D 1143 has been thoroughly updated, with paring of outdated information, inclusion of newer instrumentation, consideration of SI units, and reorganization to the current D18 format and caveats.
The following are the biggest changes to D 1143, according to Bullock:
• Requirement for the use of a load cell instead of relying solely on a jack pressure calibration for loads above 900 kN (100 tons);
• Strong encouragement to obtain a failure load, which helps economize the foundation design, rather than just testing to twice a conservatively computed estimate of the design load; and
• Extension of method to include newer types of deep foundations like auger cast piles and any type of foundation that behaves similarly to a driven pile.
Geotechnical and structural engineers, building code officials, and state, military and federal agencies are among those who regularly use D 1143.
“This test provides the ‘ground’ truth for deep foundation capacity,” says Bullock. “There are other tests that provide similar results for design purposes, but they provide only estimates of static capacity, not the actual value. This test checks the veracity of the design process.”
In addition to the D 1143 revision, Bullock says that D18.11 is working on a revision of D 4945, Test Method for High-Strain Dynamic Testing of Piles, as well as proposed new standards on the statnamic test and the Osterberg cell.
Technical Information: Paul Bullock, GRL Engineers, Gainesville, Fla.