Sonar Caliper testing is performed for drilled shaft and rock socket excavations prior to placement of the shaft reinforcing steel and concrete. The purpose of the test is to access overall alignment of the excavation, alignment of the casing, compute anticipated concrete volume, assess the potential for side wall cavities in the rock socket and overall bottom of excavation cleanliness.

The test is done with a water or slurry filled excavation by using a sonar (acoustic) head with data typically collected at 6 or 12 inch intervals from the bottom to the top of the drilled shaft and rock socket excavation. The data is typically processed within 24 hours and prior to placement of the reinforcing steel and shaft concrete. This is done to provide the contractor with the opportunity to adjust the shaft installation procedures. In some cases where voids (typically solution cavities from karst) are present the rock socket excavation is remediated by placing lean concrete and re-drilling prior to shaft installation to avoid the potential for loss of tremie seal during final concrete placement.

FTC has had extensive experience in providing Sonar Caliper testing for karst delineation that has proven to be both accurate and reliable as has been demonstrated when using subsequent additional verification methods such as underwater video observation.