Crosshole Sonic Logging (CSL)
The CSL method uses the propagation time and relative energy of an ultrasonic pulse between parallel access tubes to check the homogeneity and integrity of concrete structures. Such structures include:
- Bored Piles
- Drilled shafts
- Concrete Piles
- Augercast Piles
- Slurry Walls (Diaphragm Walls)
- Dams, Barrettes, etc...
Testing is performed using two ultrasonic probes, one transmitter and one receiver, placed within vertical access tubes, plastic or steel, installed before pouring concrete or within boreholes drilled into the structure after concrete has cured. The probes send and receive an ultrasonic signal that travels between the access tubes or boreholes through the concrete structure. In high quality concrete this signal will travel with a velocity of approximately 12,000 ft/s - 14,000 ft/s, however, the presence of the following within the structure will disrupt the signal causing a decrease in signal velocity:
- Soil Inclusions
- Gravel
- Water
- Drilling mud
- Bentonite
- Voids
- Contaminated concrete
- Cracks
- Necking
Within drilled shafts, several CSL tests are performed between a
number of access tubes spaced evenly around the structure to
adequately test all concrete within the rebar cage. This also makes
it possible to determine the approximate size of the defects listed
above.
Earth Dynamics performs CSL testing in accordance with ASTM D6760-02
"Standard Test Method for Integrity Testing of Concrete Deep
Foundations by Ultrasonic Crosshole Testing".