Testing Grout Seals with an Ultrasonic Probe

In a 1996 report, I described the problems we had found with the use of rotary drilling mud & cuttings slurry as a grout. I reported we planned to continue to study these problems, working with Professors Tuncer Edil and Craig Benson of the University of Wisconsin-Madison Department of Civil & Environmental Engineering. They had developed a down-the-hole ultrasonic probe to evaluate the integrity of grouts. (Photo 1)

Within the past couple years, their graduate students successfully used this probe to test the grout seals of water wells constructed with rotary mud-circulation methods. They first tried to use the probe in steel-cased wells. It did not work because the transducer signal was completely scattered by the rough inner surface of the steel casing and would not penetrate through it. They were able to test wells installed with 5-inch diameter thermoplastic (PVC) casing. PVC casing has a smooth inner surface, so the transducer can be firmly seated against it. The ultrasonic signal 1s not scattered and passes easily through the PVC casing wall.