Ultrasonic Investigations

Ultrasonic studies are used for non-destructive testing of materials and in situ investigations of small volumes around critical structures or excavations.

• Ultrasonic methods can utilise both passive and active surveys to interrogate a rock mass or concrete structure.
• Acoustic Emissions (AEs) are sound waves emitted by microcracks as they are created or move in brittle materials. Recorded data can be processed using many of the same methods employed for larger seismic events.
• AE results are often used in conjunction with ultrasonic surveys to delineate and then quantify the damage within the material.
• Ultrasonic surveys employ an array of receiving and transmitting transducers to assess the changing properties of a material under investigation.
• Processing of the data provides information on changes in material properties. Parameters such as Young's Modulus, Poisson's ratio, crack density and saturation can be deduced from the data.

Ultrasonic monitoring employs an array of receiving and transmitting transducers to assess the changing properties of a material under investigation. These methods are routinely used to monitor rock and concrete samples.

Short pulses (~100 µ s duration) of energy are transmitted into the material and, by measuring the precise time of flight between the pulser and receiver, an accurate P- (and S-) wave velocity over the ray-path can be computed. If the acquisition system records full waveform data, then the waveform amplitudes can also be investigated.

Processing of the data provides information on changes in material properties. Parameters such as Young's Modulus, Poisson's ratio, crack density and saturation can be deduced from the data.
Monitoring campaigns typically make use of regular, repeated, measurements between fixed sets of transmitters and receivers. When used in the laboratory, the transducers are fixed to the sample or contained with the platens. In situ measurments are made from boreholes or, in the case of concrete, can be directly buried.

Processing of the data provides information on changes in material properties. Parameters such as Young's Modulus, Poisson's ratio, crack density and saturation can be deduced from the data.