Crosshole Sonic Logging (CSL) is the most accurate and reliable Quality assurance (QA) technique for assessing the integrity of deep foundation elements constructed on-site from concrete or grout. The method is mostly used to assess geometrical and structural soundness of newly placed drilled shafts, auger cast piles and similar substructures such as slurry walls and mat foundations.
In accordance to ASTM D6760-02, “Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing” we conduct the CSL method in access tubes (steel or PVC) of 1.5-inch I.D. or greater which are tied to the rebar cage and pre-cast into the shaft at the time of construction.
CSL test relies on propagation of ultrasonic waves between two or more access tubes to measure the velocity and signal strength (amplitude) of the propagated waves. Alternatively, the test could also be conducted through post-casting drilled core holes aligned in geometry as the test holes.
Single-Hole Sonic Logging (SSL) can also be used on smaller diameter drilled mini-piles and auger cast piles. The single hole sonic logging method is used in cases where only a single access tube can be placed in
Crosshole Sonic Tomography
Defects found by CSL may be further resolved by Crosshole sonic tomography techniques for 2D / 3D analysis for locating anomalies / defects, location, depth and lateral extents.