Case Histories Utilizing Thermal Integrity Profiling for Foundation Quality Assurance

Marty Bixler

Dans les comptes rendus d’articles de la conférence: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: CASE HISTORIES - III Miscellaneous

ABSTRACT: Advances in Quality Assurance and Quality Control (QA/QC) of foundation elements, including drilled shafts and Augered-Cast-In-Place piles, have been achieved using Thermal Integrity Profiling (TIP). This Non-destructive testing (NDT) method utilizes the heat generation of curing concrete to assess drilled shaft shape and overall quality. Temperature measurements along the length of an element are recorded during the concrete hydration process following placement. These temperature measurements along with volume information and installation details can be used to model the effective shaft radius and shape. Recent TIP projects have displayed evidence of local anomalies within the collected data. This paper presents several case histories on projects where TIP was implemented and compared with additional field verification measurements, and provides an evaluation and discussion of project outcomes.

RÉSUMÉ: Des avancées en matière d'assurance qualité et contrôle qualité (QA/QC) des puits forés et pieux forrés cimentés ont été atteintes grâce à la technique du profilage thermique (Thermal Integrity Profiling TIP). Ce test non destructif (NDT), basé sur la mesure de dissipation thermique du béton en phase de curagpieux cimentés. Le principe repose sur des mesures de température à intervalles reguliers le long du pieu, ainsi que sur u. Cet article présente différents cas ou le TIP a été utilisé, et compare les résultats ave 1 INTRODUCTION Drilled shafts and Augered Cast-In-Place piles are commonly utilized as deep foundation elements on projects across the world. They are popular choices due to the high axial and lateral capacities that are obtainable. However, due to the construction procedures and installation techniques required to install a drilled shaft element, the final in place product is often difficult to impossible to inspect. Improper drilling techniques, poor concrete quality, weak and saturated soils, and improper concreting techniques may all contribute to the formation of defects and anomalies within these deep foundation elements. Quality assurance is critical to ensure the placed foundation meets the intended design parameters. When deep foundations are utilized, they often consist of concrete or grout, which is cast directly at the service location. Consequently, this type of foundation does not easily lend itself to visual inspection for structural integrity. Although several Quality Assurance / Quality Control (QA/QC) methods are available to assess structural integrity, this paper will highlight the results of Thermal Integrity Profiling (TIP). This method is performed in accordance with ASTM Standard D7949. Thermal Integrity Profiling involves collecting temperature measurements at many locations within the freshly cast deep foundation. The basic objective is to measure the heat generated by the chemical hydration process of the cement, which is dependent primarily on the chemical composition in the concrete and the mass of the various components. (Mullins et al, 2005, 2007, and 2011). Ideally, the temperatures should be collected at the time, or just prior to, when the maximum temperatures are produced (due to the heat of hydration of the curing cement). Since this normally occurs within 8 to 48 hours, after casting, depending on the shaft diameter, the most common method of data collection is by utilizing Thermal Wire® cables that are secured to the full-length rebar cage. The Thermal Wire cables contain digital temperature sensors equally spaced (approximately every 0.3 meters). The number of Thermal Wire cables applied to the rebar cage usually depends on the nominal dimension of the concrete, with each cable typically paired with another placed on the opposite side of the cage. This paper presents several examples demonstrating the use of TIP, and information that can be obtained from the results. 2 CASE HISTORY #1 Construction of the new Ocosta Elementary School in Westport, Washington State consisted of a new building, including a gymnasium with an approximately 40-foot tall roof structure. Due to the site being located in a potential tsunami zone, the roof is to serve as a tsunami refuge (vertical evacuation) structure and the foundation is

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