Crosshole Sonic Logging – CSL

Bored pile construction is inherently difficult and requires extensive process-quality assurance. 

CSL-testing as a quality control measure provides complementary information to other control activities such as borelogs, concrete logs and low strain integrigty tests.

It is carried out by pulling a pair (or pairs) of ultrasonic transmitter and reciever probes in preinstalled tubes placed along the rebar cage. Alternatively it can be performed by means of cored channels prepared after construction.

The ultrasonic pulses are recorded and converted to an electrical signal, stored and analysed off-site and interpreted for parameters indicating local concrete quality.

 

CSL-testing provides information about:

• First Arrival Time (FAT) of the ultrasonic pulses travelling through the concrete located between the tubes at a particular location of the pile
• Releative energy of the ultrasonic pulses travelling through the concrete located between the tubes at the same location.
• By comparing the two measure values with reference values, they aid in identification of anomalies, flaws or defects if present in the pile

The FAT-value can be used to calculate wave speed, which is an indicator of concrete strength. The relative energy is an indicator of concrete quality and whether blemishes are present. 

The location and extend of anomalies, flaws, or defects can further be illustrated by means of tomography diagrams to aid e.g. considerations of root causes and remedy measures.

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