Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
ALTERNATIVES TO LATERAL LOAD TESTS
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| 12.8 ALTERNATIVES TO LATERAL LOAD TESTS Lateral load tests may not be appropriate for all projects. For example, typical simply supported bridges with short spans for highway projects may not require lateral load tests, not only because the lateral loads may not govern the design, but the costs involved may not be justified fora small number of foundation elements. Alternatives to lateral load tests include the use of more in-depth investigations including the use of in-situ testing or use of available p-y curves from other projects in the same or similar geology. In-situ testing methods can be used to develop site-specific p-y curves. Several in-situ test methods can be used in a variety of materials as discussed in Chapter 3. An extensive in-situ testing program may still be significantly less expensive than a full scale lateral load test program, and may therefore be a more effective use of resources. Such in-situ testing can be performed during the design phase, and therefore the project can benefit from having this data at an early stage. Site-specific data can also be compared and correlated with similar types of data from other areas where actual lateral load tests have been performed. 196 Local experience maybe available for typical bridges in similar ground conditions that have exhibited satisfactory performance during service. If local practice or precedent has a well-established basis for design, lateral load tests may not be required. In some areas, lateral load testing may have been performed at other projects or as part of research programs. Several research programs have been performed to investigate lateral load testing of drilled shafts in local conditions (refer to Chapter 4 for examples. The results of such research programs or other load tests in the project area or geologic formations can be used if considered consistent with the project conditions. In areas where there is limited local experience, reference to lateral load tests in similar subsurface conditions from case histories published in the engineering literature may provide insights that are helpful to a designer. It is important to note that when using p-y curves or data from other tests, locations, or geologic conditions, there is an element of risk or uncertainty that is introduced in the design. Even using in-situ testing to develop p-y curves should be considered to have greater uncertainty or risk than a full scale lateral load test. Therefore, when using alternatives to lateral load tests, consideration should be given to using input soil/rock properties for design that are less than what would otherwise be used if lateral load tests are specified to verify foundation performance. Any adjustment to input parameters will rely on the judgement of the designer, considering the type materials at the site and the variability in their geotechnical properties, among other considerations. This approach should result in a more robust design that provides the required foundation performance invariable or uncertain ground conditions. Often, this approach will have little or no impact to the foundation arrangement or cost. |