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Picture 7

the following scheme shows (left) the principle of the wire-line drilling system in generał and of the CPTWD in particular:

has been modified in a way to make it suitable to keep a CPTU cone, a security system, etc., inside itself. The so called core-barrel, is of the "fixed head" type. It rotates with the casing so that the bottom part breaks up the soil. It is similar to the type used in gravel. At the bottom, there is a drillbit of special design.

The following,Picture 7, shows how the mud flows (at a maximum pressure) through the openings of the drill-bit and between the drillbit and the intemal side ofthe

Picture 8

Safety device. Inside the "core barrel", the CPTU cone is assembled in a device which allows it to “return” into the core barrel when the resistance is greater than a pre-set maximum value.

Picture 9,.shows the CPTU cone after its retrieval at

Picture 9

3 RESULTS OBTAINED WITH THE CPTWD 3.1 Parma zonę (July 2000)