Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
Recommendations Regarding P-y Method
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| 6.3.4 Recommendations Regarding P-y Method The p-y method is recommended for use in laterally loaded deep foundation analyses. Although this is an empirical method and there are theoretical shortcomings, the method has been widely and successfully used in a variety of subsurface conditions. There is a high degree of confidence in the results for most typical applications involving the use of deep foundations that are long enough to be governed by deflection rather than rotation. A number of lateral load tests and research projects have been performed to investigate, confirm, and refine p-y curves for various soil and rock conditions (refer to Appendix E. Most agencies and practitioners are therefore familiar with its principles and use, and have confidence in the results obtained using this method. Summary points regarding the use of the p-y method include Commercial software can be used to perform p-y analyses, as it is generally easy to use and produces results quickly. The inputs of the p-y method typically include loading conditions (magnitude, type, and location of loads, subsurface conditions (soil or rock layer depth, thickness, density, strength and groundwater depth, and geometry (ground slope, foundation embedment, and exposed height of foundation element. 75 The outputs of the p-y method include distributions versus depth of lateral displacement, shear forces, bending moments, soil resistance, and soil and pile moduli. The analysis of deep foundations using the p-y method should include parametric evaluation of key input parameters to assess the potential sensitivity of the results to such inputs. Most commercial software programs include a wide variety of p-y curves for various geomaterials, allowing the practitioner to reasonably model real-world conditions. • Site-specific or project-specific p-y curves can be developed based on lateral load tests 6.4 STRAIN WEDGE MODEL The strain wedge model (SWM) (Ashour et al. 1988) was developed to provide a theoretical basis for correlating lateral soil resistance and pile/shaft deflections compared to the predominantly empirical p-y method. The SWM method is an approximate methodology that incorporates the stress and strain responses as well as strength (drained or undrained) of soils. This soil behavior occurs in a hypothetical D passive wedge of soil mobilizing strength behind a single pile/shaft to derive resistance, as illustrated in Figure 6-7. The soil resistance is based on a limit equilibrium solution of passive earth pressure within the D wedge. Download 6.03 Mb. Share with your friends:
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