Cross-Hole Sonic Logging (CSL] allows for the detection of concrete defects such as poor quality concrete, soil inclusions, voids, honeycombing and slurry inclusions. This method is applicable to piles of any dimensions and can be used on diaphragm wall or any similar concrete structures. It gives indications of the concrete quality down the entire pile shaft; it does not however provide information about the concrete outside the reinforcement cage and does not clearly identify the type of detected defect.
CSL is achieved by the use of sonic transmitter and receiver probes which are lowered down the pile shaft through pre-installed access tubes. An ultrasonic pulse generator sends pulses to the transmitter probe where they are converted into ultrasonic waves that are received by the receiver probe. The propagation time of the ultrasonic signals between the tubes is measured and stored while the meter-wheel provides the corresponding depth. Variations in signal arrival time and strength indicate areas that may require further investigation.
