Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
Lateral Load Tests in Construction to Verify the Design
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- 12.1.3 Considerations regarding Subsurface Characterization for Lateral Load Test Program
| 12.1.2 Lateral Load Tests in Construction to Verify the Design Lateral load tests maybe required in construction in order to verify the adequacy of the design. This maybe done to reduce risk, particularly where there is greater uncertainty regarding design parameters. Performing lateral load testing in construction maybe simpler from a procurement standpoint, especially for design-bid-build, because it does not require a separate contractor expense during the design phase. If inadequate performance of the foundation is considered a significant risk or possibility, then the specifications should require that the lateral load testing be performed and results provided within a certain period of time prior to ordering or mobilizing material and additional equipment for production work. This will help mitigate some of the cost impacts that may result from changes in the foundation design. The risk of redesign during construction can be further mitigated by providing a more robust foundation design that considers less favorable site conditions rather than average conditions. 177 12.1.3 Considerations regarding Subsurface Characterization for Lateral Load Test Program Subsurface exploration and testing fora lateral load test program should be planned and performed in accordance with approaches described in Chapter 3. Focus should be placed on characterizing the ground profile and engineering properties of the near surface soil (and rock) as it is in this zone that most of the resistance to lateral loads will need to be derived. That is not to say that the characteristics of the deeper strata can be ignored. These strata are also important for defining the p-y response and for assessment of foundation fixity. If the foundations are long, and rely on rock sockets at depth for lateral resistance, then the strength, stiffness and rock mass characteristics (e.g., RQD, orientation of discontinuities, nature of infill, presence of clayey gouge, weak laminated inter-beds, anisotropy) are particularly important. If the lateral load tests are for research purposes, then it is recommended that a detailed program of advanced in-situ and laboratory testing be performed at the load test site to provide a means by which to correlate p-y curve responses to ground engineering parameters (e.g., Simpson and Brown 2003). If the lateral load testis performed as part of a project, then there must bean adequate level of investigation at both the test location and the production foundation locations to be sure that the subsurface conditions at the test sites) are representative. The groundwater conditions likely to prevail during the life of the structure need to be considered in planning the lateral load test. Depending on the time of year that the tests) is done, the seasonal groundwater level maybe lower than the elevation that will occur at other times of the year or during flood events. In conditions such as this, it is desirable to saturate the soil at the test location prior to the test, if practical to do so. An example of this was presented by Dunnavant and O’Neill (1989) who performed lateral load tests on open-ended steel pipe piles and drilled shafts in the over-consolidated Beaumont Clay of Houston, Texas. Five months prior to installation of the foundation elements, the test pits in which construction would occur were intentionally flooded with water. During the load tests, these pits were maintained in the submerged condition. Any anticipated changes in the site conditions at the production foundation locations, such as placement of fill, cuts, or removal and replacement of unsuitable soils (soft soils, etc) should be considered in the design of the test pile program and, where practical, such changes should be incorporated into the test program. Download 6.03 Mb. Share with your friends:
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