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

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Broms Method:
Broms (ab) for estimating lateral capacity and deflection based on the strength properties of the soil and the structural stiffness. Short piles and long piles are analyzed differently based on formulas employing the soil subgrade reaction modulus and pile/shaft properties.
Reese Method:
FHWA-IP-84-11 for piles and drilled shafts (1984). This method is based on the p-y methodology and presents the critical penetration concept, more commonly referred to as critical depth, defined as the depth at which increasing pile length does not result in decreasing head deflection. See Figure E- 1.
Figure E- 1: Influence of embedment depth versus head deflection (Reese 1984).
Deep Foundation Elements:
Long, vertical, or near-vertical foundation elements with significant length to width ratio, generally consisting of piles, drilled shafts, auger cast piles, micropiles, or similar elements. For the purposes of this document, the terms drilled shaft and pile are referenced as appropriate according to the source material, but the concepts are considered universal, with a dependence on the diameter and relative stiffness of the element, regardless of the actual type of element or installation method.
P-y Curve Methodology:
Represents soil-pile interaction as a series of nonlinear one-dimensional springs.
Strain Wedge Model (SWM) Method:
Uses conventional soil strength parameters to characterize the resistance of a three-dimensional passive soil passive wedge and develops p-y curves for analysis as a one-dimensional beam on elastic foundation

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4. STATE DOT RESEARCH METHOD
As part of the literature review, all 50 DOT websites were visited to find available documents related to design of bridges, noise barriers, luminaries, and other transportation related structures. Specific documents considered relevant consisted of bridge design manuals and geotechnical manuals. Each website was searched for these documents. Abridge design manual or guidance document was located for 35 states, but only 15 had a geotechnical manual or guidance regarding geotechnical design. Additionally, the websites were searched for keywords commonly associated with lateral design of deep foundations. This additional search resulted in 10 design recommendations or memoranda specific to the topic under consideration that have been issued by the DOT but not incorporated into specific design manuals as of the time of the research. The level of detail and guidance provided in the manuals and other documents varies. It is recognized that related documents from the various states may exist, but were not revealed by the method of investigation, or that some of the documents that were found maybe obsolete, superseded or in the process of being replaced. Nonetheless, based on the quantity of information revealed online, we believe the basic intent to document the state of DOT practices has been met based on the data set investigated. Additional information may exist in offline DOT sources, but would not be expected to differ significantly from the information summarized herein. In addition, unpublished or offline sources may still be under review or revision and may not be final, and therefore may not reflect the current state of the practice. Additionally, the results of a 2007 national survey of State DOTs were provided by the FHWA, including brief descriptions of the respective State’s design approach for lateral analysis and displacement limits for deep foundations. Puerto Rico and Federal Lands were included in that survey, but were not included in the web-based research.

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