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![Non destructive Investigations Non destructive Investigations](/images/visuels/public/2_how/3_operation/2_auscultation/2_non_destructives_1.jpg)
Non-destructive investigations are those undertaken without damage to the lining. They virtually enable to carry out a continuous inspection of a facility and in particular to detect abnormalities that afterwards must be investigated in a destructive way using all appropriate means.
Special emphasis must be placed on non-destructive investigations as they cannot be used alone but associated with trial borings. In addition. non-destructive investigations may be used to specify the location of the trial borings and thus to improve their representative character.
![Breval Tunnel - Microgravimetric Endoscopy (MGE). Regression to 11 densities. Breval Tunnel - Microgravimetric Endoscopy (MGE). Regression to 11 densities.](/images/visuels/public/2_how/3_operation/2_auscultation/2_non_destructives_2.png)
- Electro magnetic wave pulse reflectometering
- Other geophysical methods
- Microseismic
- Microgravimetry
- Electric methods
- Infrared Thermography
- Ultrasounds
- Internal Jacking test