Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities

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hif18031
Soldier Rev B

Block 11 – Perform Group Analysis of Laterally Loaded Deep Foundations

Block 10 – Perform Axial Design
The minimum design length and size for axial capacity must be determined. The minimum pile/shaft penetration will be the greater of
1. The penetration required for axial design,
2. The penetration required for lateral loads, and
3. The penetration required to meet settlement criteria. Typically, approximate analysis is initially done to estimate the pile/shaft size for lateral loading. This element size is then used for axial load analysis, with depth increases as needed for axial resistance. In many cases, an iterative process maybe needed to arrive at a final design that satisfies both lateral and axial loading criteria. Axial foundation design is not addressed in this manual. For axial capacity considerations and design guidelines refer to Hannigan et al. (2016), Brown et al. (2010), Brown et al., (2007), and Sabatini et al.
(2005) for driven piles, drilled shafts, CFA piles, and micropiles, respectively, as well as the current version of the AASHTO LRFD Bridge design specifications.

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Block 11 – Perform Group Analysis of Laterally Loaded Deep Foundations
For designs that include groups of piles/shafts, the analysis of the group must betaken into account because of overlapping zones of influence of the foundation elements and the influence of frame action on the load distribution within the group. In many cases, the interaction of foundation elements can be accounted for by including appropriate reduction factors in the analysis of a single pile (p-multipliers in p-y analyses, as discussed in Chapter 7). However, for complex foundations or for complex soil–structure interaction, an analysis of the pile/shaft group lateral resistance and deflections should be performed. This is most often done using computer software as discussed in Chapter 7. Similar to the steps outlined above, this should be checked for Geotechnical and Structural Strength, Service, and Extreme Limit States. Results of the group analysis may result in revisions to the pile size, depth, or layout, and therefore may require iteration with the previous steps.

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