Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
Considerations for Test Pile Location
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| 12.1.4 Considerations for Test Pile Location The selection of the test locations) should be made such that the ground profile is representative of the less favorable ground and groundwater conditions into which the production piles/shafts will be installed. In considering what is representative, emphasis should be placed on the upper strata, say within 5 to 10 diameters of the ground surface, excluding any depth of possible soil disturbance or scour. It is typically in this zone that a pile or drilled shaft will need to derive most of the lateral resistance to load, and it is also the zone in which bending moments will likely be highest. Unfortunately, the uppermost soil layers are often those least sampled and tested in subsurface exploration programs, and are typically very variable in terms of composition and consistency. Often it is the deeper bearing strata that receive most attention because it is in the deeper zone where foundation elements will achieve resistance for axial capacity. Specifications for subsurface exploration should require sampling in the near surface with appropriate laboratory testing to characterize the strength and stiffness properties of the ground for laterally loaded pile/shaft analysis. These near surface data are essential for correlating the p-y response from the load test to the site-specific conditions. 178 For rock socketed foundation elements, such as drilled shafts, the depth and quality of rock at the test location should be representative of the less favorable rock conditions that maybe encountered at the production foundation locations. Testing rock that is less weathered, stronger, higher quality, shallower depth, or otherwise more favorable compared to production pile/shaft conditions may produce test results that are unconservative for design and may not assure required foundation performance at the different foundation locations. Rock sockets for test foundations should be similar to the socket lengths anticipated for production foundations. Given the test piles or shafts will likely be sacrificial, it is important to locate them and the reaction system where they will not pose an obstruction to the proposed foundations of the permanent works, recognizing that the locations of the permanent foundations may not be known at the time of planning the test. Download 6.03 Mb. Share with your friends:
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