Thermal Integrity Testing of Drilled Shafts

Drilled shaft foundations have historically been plagued with construction related defects (i.e., soil inclusions or poor concrete cover) that most often go undetected due to the blind construction techniques necessary. These defects can affect the quality of the bond interface between the shaft concrete and the insitu geomaterial as well as the durability of the reinforcement. This project investigated the merits of a new easy-to-use method of assuring shaft integrity via infrared thermal detection methods that can assess the presence or absence of intact concrete both outside and inside the shaft reinforcement cage. The objectives included (1) field temperature measurements of mass concrete structures with specific interest in drilled shafts and (2) numerical modeling to verify the anticipated temperature response within a drilled shaft or mass concrete structure. Both small scale and full scale shafts were constructed and monitored during the curing/hydration phase. The temperature measurements obtained were used to verify the presence of anomalies while also obtaining temperature dissipation information to the surrounding materials. These case studies were used to calibrate a 3-D thermal modeling software developed expressly for mass concrete conditions with emphasis on drilled shaft integrity evaluation. Further evaluation of these sites along with case studies from larger diameter shafts showed that mass concrete conditions could be experienced by shafts even when small in diameter. Using the new thermal modeling software, the physical dimension of the test shafts as well as the location of known anomalies were inputted and signal matched against the measured temperature traces. The good correlation obtained showed that forward modeling shafts could be used to predict the size and location of anomalies. Inverse modeling algorithms were also developed with encouraging results. Finally, prospective construction techniques using voided shafts were conceived, modeled, and evaluated for feasibility. Initial results indicate that benefits could be derived from both mass concrete temperature control and reduction in concrete volume/usage.

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 232p

Subject/Index Terms

Filing Info

  • Accession Number: 01054060
  • Record Type: Publication
  • Contract Numbers: BD544-20
  • Files: TRIS, STATEDOT
  • Created Date: Jul 16 2007 11:46AM