To fulfill the sounding of the underground garage in Moscow there was used a production-run specimen of Rascan radar. The task was to detect places of the water proofing faults in the walls and ceiling structures of the garage, whose construction had been actually completed, and the project was being prepared for acceptance by the customer. The work was performed in the end of the winter of 2001. The winter was rather warm and water from melted snow began to enter the soil.

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Operators with the
Rascan radar during
the wall examination

Figure shows operators with Rascan radar during the examination. In this photo one can see the operator with the radar microwave head when sounding the wall of the underground garage.

Figure below shows microwave images of the wall area, received in two cross polarizations. At the top of the left microwave image the bright spots are visible, which correspond to the areas of increased moistening. The spots are surrounded with a dotted line in the image for convenience. The given spots were supposed to coincide with hidden cracks in the wall.
Microwave images of the wall area containing spots
corresponding to the places of increased moistening
on two cross polarizations

Figure below shows a worker opening the crack. Water down-flows on the wall resulted from water flow through the crack after it had been opened. Then the crack was sealed with hermetic grout. The leak-proofness of the wall was restored after the completion of the work.

Opening the crack
Sealing the crack
with wet seal grout

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The operator
the ceiling ledge
with help of the
Rascan radar

Another object of examination was a ledge on the garage ceiling. In the foreground of the picture one can see Notebook type computer, which was used to display the radar's images. After scanning a part of the ledge the microwave images in figure below showed a crack of a intricate shape, which could result in water infiltration. In the builders' opinion this crack in the concrete structure also needed sealing.

Microwave images of the part of the ceiling ledge showing spots
corresponding to the places of increased moistening
in two cross polarizations

The fulfilled investigations have also shown that Rascan holographic radar can become a useful means of nondestructive testing of underground construction quality as well as a means of detecting cracks in structures and potential places of soil water leakage in cases when water started already to enter these cracks.


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