Crosshole sonic logging (CSL) is a method to verify the integrity of drilled shafts and other concrete piles. This method is considered to be more accurate than sonic echo testing in the determination of soundness of concrete within the drilled shaft inside of the rebar cage. This method provides little indication of concrete soundness outside the cage.
Also known as Crosshole Acoustical Testing, CSL normally requires steel (preferred) or plastic tubes installed in the drilled shaft and tied to the rebar cage. After the shaft is drilled, and before the rebar cage is placed in the hole, plastic or, ideally, steel tubes are attached to the interior of the rebar cage and then the cage is lowered into the hole and the concrete is placed.
After the concrete has cured, the tubes are filled with water as an intermediate medium, and a sound source and receiver are lowered, maintaining a consistent elevation between source and sensor. A signal generator generates a sonic pulse from the emitter which is recorded by the sensor. Relative energy, waveform and differential time are recorded, and logged. This procedure is repeated at regular intervals throughout the pile and then mapped. By comparing the graphs from the various combinations of access tubes, a qualitative idea of the soundness of the concrete throughout the pile can be gleaned.
A more advanced, higher-end analysis that creates a mock 3-dimensional graphical display of the concrete soundness throughout the pile is known as Crosshole Sonic Tomography.
References
- Farouz, E., Landers, P., Webster, S., November, 2005. Case History: Foundation Evacuation for the Virginia Highway 288 Project. GEO3 Construction Quality Assurance/Quality Control Technical Conference: Dallas/Ft. Worth, TX; 49-60.
- Beim, J.W., Debas, L.F., Kormann, A.C.M., Martinati, L.R., Neto, L.A., November, 2005. Tomography: A New Technology for Quality Control of Deep Foundations. GEO3 Construction Quality Assurance/Quality Control Technical Conference: Dallas/Ft. Worth, TX; 323-328.
See also
- FHWA Drilled Shaft Tutorial Chapter 10
- CSL paper from the 2003 symposium for Nondestructive Testing in Civil Engineering
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