Study of rock inhomogeneity with ultrasonic tomography using concrete block and limestone block at laboratory scale

摘要

Ultrasonic wave propagation test is a non-destructive test that can be used to detect inhomogeneity of rock. Time of Flight (ToF) of ultrasonic wave was measured by direct method through the interior of block, using PUNDIT device (Portable Digital Indicating Non-destructive tester) with transducer of stress wave in ranges of frequency 80 kHz. Two reconstruction algorithms have been used, namely, the tomographic ART algebraic reconstruction technique and the SIRT simultaneous iterative reconstructive technique, in order to represent a contour map of ultrasonic velocity distribution within the block observed. All the tests were conducted at laboratory scale on several blocks, such as concrete block with artificial void, concrete block with artificial discontinuity, and limestone block with two artificial holes, furthermore the ultrasonic method were applied to detect these conditions. The results show that the tomographic algorithm is proven as a tool to detect the inhomogeneity of the block.