Thermal Integrity Profiling and Crosshole Sonic Logging of Drilled Shafts with Artificial Defects

摘要

Two 1.5 m (5 ft) diameter drilled shafts with lengths of 25.9 m (84.9 ft) and 23.5 m (77.0 ft) were constructed with artificial defects and tested by thermal integrity profiling (TIP) and crosshole sonic logging (CSL) methods. Prefabricated artificial defects consisting of low-strength precast concrete cylinders in the first shaft and plastic molds containing aggregates, sand, and water in the second shaft were secured to the inside of the rebar cages at two depths on each shaft. The defects constituted approximately 4% of the shaft cross-sectional area for the first shaft and 8% for the second. Both test methods clearly indicated the presence of the O-cell, while neither method strongly signaled the presence of the smaller defects. The larger defects were detected by CSL testing, and resulted in minor local temperature reductions in TIP tests. The study indicates a possible lower bound resolution of at least 8% of the shaft cross sectional area for a defect to be reliably detected by TIP.