Cross Hole Sonic Logging (bored and auger piles)
Cross Hole Sonic Logging (CSL) verifies the structural integrity of drilled shafts and other concrete piles. It offers increased accuracy than sonic echo testing in determining structural integrity soundness of concrete within the drilled shaft inside the circumference of rebar cage.
How it Works
1. Access Tubes Installed
Installed before construction and filled with water, Access Tubes are typically 38 to 50mm diameter PVC or steel tubes tied to the inside of the rebar cage. The number of tubes depends on structure size and resolution required.
2. Readings Taken
After being lowered to the bottom of separate tubes, the source and receiver hydrophones are simultaneously lifted to measure the horizontal ultrasonic pulse velocity. The depth wheel controls the sample reading resolution, typically taken at 6cm intervals.
3. Results Interpreted
Uniform, good quality concrete promotes propagation of ultrasonic waves while voided, poor quality concrete gives longer ultrasonic wave travel times and lower amplitudes. A complete loss in signal means a substantial void is hindering the transfer of the signal between the hydrophones.