Single Hole Ultrasonic Test (SHUT)
SHUT (Weltman 1977) is a derivative of crosshole testing, standardized in ASTM D6760-16. It was originally developed for cases where the pile was checked by core drilling, in order to increase the range of the inspection. The special combined transducer produced for this purpose had a diameter of 55 mm and a length of not less than two meters. The system reportedly succeeded in discovering defects, but because of its bulk was subsequently abandoned.
The SHUT was described in more recent literature (Brettman & Frank 1996), this time with separate transducers of the type used in crosshole testing (Figure 2). The tubes used were either plastic or steel, and the authors reported the detection of planned defects covering between 25% and 64% of the pile's cross-section. No details were given about the spacing between the transducers.
Brettman et al. (1996) performed SSL tests on an augered cast in place piles, using both PVC and steel tubes. Some of the tests were carried out in wet grout, immediately upon completion of grouting, and the authors claimed success in locating planted defects. However, in a more recent publication, the first author (Brettman 2000) recommends that testing be done in PVC tubes, and at an optimal age of three days.