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Ultrasonic Monitoring of Shaft Excavation

31ASC was involved in an ultrasonic investigation into the extent and evolution of the excavation-damaged zone (EDZ) during the excavation of a shaft at ANDRA’s Meuse/Haute-Marne Underground Research Laboratory in France. The presence of damaged zones around deep excavations could provide preferential pathways for stored material towards the biosphere; therefore the study of the EDZ is of high importance in the context of deep geological storage or disposal of nuclear waste. The methods and results of this investigation have been published in Volume 46 of the International Journal of Rock Mechanics and Mining Science:

Balland C., Morel J., Armand G. and Pettitt W. Ultrasonic velocity survey in Callovo-Oxfordian argillaceous rock during shaft excavation. Int. J. Rock Mech. Min. Sci., Vol 46, 69-79 (2009).

The experiment was performed at depths between 465 and 475m in an argillaceous rock mass. The study defines the spatial extent of the EDZ and investigates its evolution as the shaft excavation front develops.

The research was carried out using an OMNIBUS system supplied by ASC consisting of 21 sensors and borehole installation frames, down-hole pulser-amplifiers, and a 16-bit, 10MHz, data acquisition unit. ASC’s InSite Seismic Processor was used to provide control over the hardware operations and fully-automated data capture. It also provides data management, visualisation and processing for three-dimensional ultrasonic surveys and acoustic emission studies.

Pulser-Amplifier System
ASC's Pulser-amplifier System

To access the abstract and full text of the article click here (external link).

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