Evaluation of Geomembranes Using an Ultrasonic Method

ABSTRACT: An ultrasonic testing procedure was developed to evaluate geomembranes. The pulse-echo inspection technique was used on the surface of geomembranes without disturbing the material. The equipment required consists of a P-wave transducer, a pulser-receiver, and a signal acquisition system. Travel time of ultrasonic waves and waveform energy are measured to evaluate the condition of geomembranes. Laboratory tests were conducted to assess the effectiveness of the method. Defects that simulate installation damage and various inservice degradation conditions were in-duced on samples. The defects were identified with the ultrasonic method at a success rate higher than 98%. Changes in the thickness or the microstructure of the geomembranes were identified. Surficial and internal defects were located. Defects that were not visible from the measurement surfaces were identified. This method appears promising to monitor the condition of geomembranes in the laboratory or in the field and to assess in situ damage to geomembranes. Geomembranes are used as barrier layers against liquid and gas transmission in various applications including liners for waste containment facilities, canals, and dams; waterproofin