Abstract:
Seth H. Hamblin, P.E., Geosciences Testing and Research, Inc.
Les R. Chernauskas, P.E., Geosciences Testing and Research, Inc.
William D. Oder, Geosciences Testing and Research, Inc.
Large diameter drilled deep foundations are a widely utilized solution throughout North America and the world. Numerous design and construction techniques developed over the past 100 years have made this type of foundation a robust, reliable, and efficient foundation option to support a wide variety of structures. From major bridges, to colossal marine structures, to high-rise buildings, drilled shafts are a time-tested choice for a wide range of infrastructure projects.
Yet, what remains ambiguous in the current state of engineering practice is how to respond when a shaft is constructed that, for potentially numerous different reasons, may or may not meet the design requirements? In this case, what are the best practices for Contractors and Engineers when a structural, geotechnical, or material integrity issue arises during construction? In our experience the answers to these questions are not widely known, but are profoundly important so that engineers can have tools available to confidently and efficiently address concerns, and provide a path forward for the project.
Using the results of several case studies, this paper seeks to answer the above questions by presenting details of how different remediation approaches, encompassing a combination of structural and geotechnical engineering methods, and non-destructive integrity testing data, were employed to evaluate the acceptance of “ questionable” drilled shafts. Through multidisciplinary techniques like Crosshole Sonic Logging and 3-D Tomography which enhance the resolution of anomalous zones and defects in concrete, the development of concrete strength estimates from non-destructive testing data, and executing innovative structural and geotechnical analyses to evaluate the as-built conditions, drilled shafts that might have historically been rejected were ultimately accepted by the project team. This paper presents a series of unique case studies that together draw a roadmap for a comprehensive approach to reliably evaluate and guide the industry to address these types of drilled shaft construction issues.