Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
LIMITATIONS OF LATERAL LOAD TESTS
Download 6.03 Mb. View original pdf
|
Soldier Rev B
| 12.7 LIMITATIONS OF LATERAL LOAD TESTS Lateral load tests are not without limitations, which need to be considered carefully when first considering the use of lateral load tests, during the planning of the test, and for applying the results in design. Limitations of lateral load tests include Use of a free head condition in a lateral load test does not replicate the behavior of a fixed head condition that often represents the connection of piles/shafts to a pile cap A load test on a single pile (or drilled shaft) does not replicate the behavior of piles/shafts in a pile group. p-multipliers need to be selected using judgment and code provisions (e.g., AASHTO Table 10.7.2.4-1). Lateral load tests on pile groups can address this limitation, but are expensive, and rarely, if ever, performed in practice 195 A lateral load testis unlikely to appropriately model a future scour condition. It is possible to model local scour with the use of an isolation casing, but the reduction ineffective overburden stress due to general scour and contraction scour typically cannot be accounted for in the test setup Lateral load tests performed during construction typically come too late to benefit foundation design lateral load tests during construction typically serve as proof tests to verify design parameters and evaluate the influence of construction means and methods Lateral load tests performed during the design phase of a project require costly mobilization for installation of a few test piles/shafts; such costs may not be justified Lateral load tests done during the design phase of a project may not be representative if different means and methods are used to install the subsequent production piles/shafts. Except fora design- build delivery method, the test program contractor will likely be different from the contractor engaged to install the permanent foundations A few load tests may not capture the variability in the near surface soils at a project site, particularly when a thick layer of fill is present Tests piles/shafts rarely, if ever, model axial loads in combination with lateral loads, yet this is the condition most likely to occur when the structure is in service and results indifferent pile/shaft stiffness and p-delta effects. • Pile/shaft performance maybe governed predominantly by the structural properties of the foundation element rather than the ground, particularly for cases with large unsupported pile/shaft length and column lengths (e.g., tall bridge bents deep foundations installed through water and • Pile/shaft deformations during the test may not be sufficient to define the full shape of the p-y curves (e.g., piles/shafts with large unsupported length may fail structurally before mobilizing the full resistance of the soil. Lateral load test may not be cost effective or needed if pile lateral resistance is controlled at the strength limit state by the structural capacity and not the geotechnical capacity. Download 6.03 Mb. Share with your friends:
|