CPT static penetrometric testing (mechanical type) essentially consists of measuring the resistance to insertion of a mechanical bit of standardised dimensions and characteristics, as it is driven into the ground at a constant speed (2 cm/sec).
In tests with the Begemann mechanical bit, the values Qc (bit resistance), Fs (side friction) and Qt (total resistance) are measured via a load cell and shown on the display of the electronic acquisition board.
Penetrometers which can be used for CPT tests
CPT Tests Penetrometers Selector Acquisition system
Manual Hydraulic Manual Automatic
100 kN TG 63-100 ■ ◇ ■ □
200 kN TG 63-200 ■ ◇ ■ □
200 kN TG 73-200 ◇ ■ ■ □
◇ Not available
In order to control the movement of the Begemann bit, the driving rods, which act on the various components of the bit, are telescopic. An enlargement ring can be installed on the external set of rods to decrease the friction on the rods, facilitating their insertion.
The load cell, which measures the driving insertion force, is installed inside a removable unit called the “selector“, which presses alternately on the inner and outer rod.
Two types of selector exist:
● Manual selector
Before starting a driving stage, the operator must manually operate a lever which prepares the selector for the command of the inner or outer rod.
● Hydraulic selector
During the driving stage the rods are operated automatically by a hydraulic command. The operator must simply control the driving movements for insertion of the rods.
Pagani Geotechnical Equipment supplies the accessories (Begemann bits, rods, load cells) necessary for performing CPT tests.