Pile Requirements Review

by FTC
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We have seen an increasing number of piling projects that have had a host of easily avoidable piling problems. The majority of these issues were created by project designers and the owners prior to project documents being issued for bid. Such issues appear mostly to have been caused by incorrectly implementing LRFD requirements (wrong geotechnical resistance factor, pile capacity requirements that exceed the allowable structural capacity of the pile, inappropriate pile installation verification methods, etc.).

Most of these issues become apparent to FTC once a contractor has engaged FTC to perform piling testing services for a project. Often when FTC has been notified about performing piling testing services, the piling has often already been ordered in accordance with the project construction documents. As an increasing number of state DOT bridge designs are now being performed by private consulting firms, the range and frequency of easily avoidable piling problems is also increasing given the less decentralized nature of the design process.

We often have to strongly advocate for our contractor clients in the cases where such piling requirements exist as many of the design firms and owner’s representatives do not have a background in pile installation or pile testing. For example, we are aware of projects where the stresses on the pile that would result in applying the requirement nominal axial load would be over 40 ksi. However, driving stresses that are needed to develop such a capacity in a driven pile are much greater and would readily exceed the total allowable driving stress of 45 ksi in a pile with a 50 ksi yield strength. Other cases involve short piling driven to hard rock. Typically the designer is focused on developing the required axial capacity during driving. However in these scenarios the concern for developing the required axial capacity should be secondary to avoid damaging the pile tip as pile stresses can be nearly double at the toe as compared to the pile head.

Ideally, FTC will be able to work with the contactor to encourage the owner and designer to make any necessary adjustments to pile installation requirements prior to performing pile installation. In cases where the designer or owner elects to not make any changes to address problems with the piling requirements at least the Contractor is in a position to mitigate their risk in the event that piling requirements cannot be met.