Objectif
WAVE PROPAGATION INTO SOFT ROCK IS NOT COMPLETELY DESCRIBED BY PURELY LINEAR ELASTIC THEORY. THROUGH SPECTRUM ANALYSIS OF A WAVE PROPAGATED INTO SUCH A MEDIUM, ONE CAN SEE THAT SEVERAL FREQUENCIES ARE SELECTED BY THE GROUND. THIS BEHAVIOUR IS NOT FORECASTED BY LINEAR ELASTICITY BUT IS RELATED TO MECHANICAL CHARACTERISATICS OF THE MEDIUM. ANY CHANGE IN THE MECHANICAL CHARACTERISTICS MODIFIES THE FREQUENCY CONTENT OF A SIGNAL PASSING THROUGH THE MEDIUM. THIS AGREES WITH THE BEHAVIOUR OF A WAVE PROPAGATED INTO A BIOT MEDIUM OR A VISCOELASTIC MEDIUM. THEREFORE ONE CAN DETECT BY SPECTRUM ANALYSIS OF PROPAGATED WAVE ANY CHANGE IN MECHANICAL CHARACTERISTICS OF A MEDIUM. AROUND AN UNDERGROUND STORAGE IN CLAY, DISPLACEMENT OR SWELLING EILL PROVOKE A SHIFT IN MAIN FREQUENCIES.
WE USE THE GENERAL CONCEPT OF CROSS-HOLE METHOD IN ORDER TO PRODUCE OR RECEIVE THE SIGNAL. PREVIOUS EXPERIMENTS CONFIRMED THAT AN IMPROVEMENT OF THE SOIL CHARACTERISTICS IS EASILY SHOWN BY THIS METHOD. ONE DETECT THE LACK OF GROUTING IN ALLUVIUM, SAND, ETC. ONE CAN DETECT A CAVITY AND ITS FILLING AFTER GROUTING. CRACKS ON PILES HAVE BEEN DETECTED BY THIS METHOD.
ONE CAN IMAGINE THAT SUCH A METHOD IS WELL ADAPTED TO DETECT ANY CHANGE AROUND A RADIOACTIVE WASTE DEPOSIT, MAINLY IN CLAY OR IN SOFT ROCK. AROUND A BOREHOLE HEATED BY A CORROSION TUBE, WE WILL SET UP A CROSS-HOLE SYSTEM AND FOLLOW THE FREQUENCY CONTENT DURING THE HEATING OF THE CLAY.
1. CONSTRUCTION OF A NEW SHOCK TRANSMITTER FOR HORIZONTAL BOREHOLE AND THREE RECEIVERS
2. BORING OF FOUR HOLES ON THE MOL SITE (CEN/SCK)
3. SETTING UP TRANSMITTERS IN THE BOREHOLES (TAKEN IN CHARGE BY CEN/SCK)
4. FIRST MEASUREMENTS
5. REALIZATION OF THE BIG BOREHOLE FOR CORROSION TUBE (CEN/SCK)
6. MEASUREMENT OF THE EFFECT OF THE EXCAVATION
7. HEATING OF THE CLAY
8. MEASUREMENT OF THE HEATING OF CLAY EFFECT
9. INTERPRETATION
Champ scientifique
Thème(s)
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France