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Mid-America Transportation Center

Evaluation of Thermal Integrity Profiling for Deep Foundations


Researchers

  • Principal Investigator: Jeramy Ashlock (jashlock@iastate.edu 515-294-6176)
  • Project Status
    In Progress
    About this Project
    Brief Project Description & Background
    Assessing the structural integrity of bridge foundations is critical to ensuring the safety of the traveling public. However, nondestructive methods currently used in practice to determine the quality of drilled shaft foundations are severely limited by their inability to provide full coverage of the foundation cross-section, particularly in the critically important region outside of the rebar cage. Thermal Integrity Profiling of deep foundations can enhance the safety of transportation infrastructure by overcoming limitations of current nondestructive QA tests.
    Research Objective
    The goal of the proposed study is to assess the accuracy and resolution of the new TIP method by employing the technique on foundations constructed with defects of known dimensions.
    Potential Benefits
    The expected results include an improved understanding of the accuracy and reliability of the Thermal Integrity Profiling method for quality assurance of drilled shafts relative to the current practice of CSL testing. Based on favorable results of prior research, it is anticipated that the Iowa DOT will adopt the method as a complement and possible eventual substitute for CSL testing. The primary product will be a final summary research report and technical brief. Any computer programs developed for enhanced analysis of the data beyond the capabilities of the commercial software may be made available to MATC or the Iowa DOT, providing that this is in compliance with TIP device patents.
    Abstract
    Assessing the structural integrity of bridge foundations is critical to ensuring the safety of the traveling public. However, nondestructive methods currently used in practice to determine the quality of drilled shaft foundations are severely limited by their inability to provide full coverage of the foundation cross-section, particularly in the critically important region outside of the rebar cage. The goal of the proposed study is to evaluate the accuracy of a new Thermal Integrity Profiling (TIP) technique for quality assurance of deep foundations. The TIP method utilizes infra-red thermal probes lowered into access pipes which are cast into the foundation to measure the heat of hydration of curing concrete. Previous studies demonstrated that the technique can detect loss of concrete cover outside the rebar cage as well as internal flaws such as cracking or voids. However, the studies did not assess the accuracy of the technique for indicating the specific location and extent of flaws.

    The proposed research is a collaborative effort between ISU and the Iowa DOT to evaluate the accuracy of the TIP method. A full-scale test shaft will be constructed with voids at predetermined locations. Measurements of shaft integrity will be compared for the new TIP method and the cross-hole sonic logging (CSL) method, which is currently the most commonly used quality assurance tool for drilled shafts. The ability and accuracy of the two techniques to detect the specific locations, size and general shape of the known shaft defects will then be assessed. It is anticipated that thermal integrity profiling will provide cost savings to state Departments of Transportation as a more economical alternative to CSL testing, or as a screening tool to identify which shafts should be further analyzed by CSL specialists.
    Project Amount
    $ 44,340.71