The Case Test (Case Western Riserve University) falls within the tests on high level deformation pole, in which shock waves are generated by a falling object; the shock waves propagation features are collected for a next analysis through a serie of sensors applied to the pole. In particular the sensor are fixed at the pole’s top and consist in two accelometers and two strain-gauges, placed in diametrically opposite position.
The accelerators and the strain-gauges gain respectively the speed and the force within the time domain. This test consists in stimulating the pole through the fall of a mallet from different heights in order to vary the impact energy and to establish the static resistance of the foundation pole by processing the measured data.
The vibrational tests consist in provoking the element excitement through an electro-dynamic vibrator, whose mass imparts a constant force to the pole’s head.
The transmitted energy proceeds towards the pole’s basis, which reflects a part of it upwards; the consequent motion of the pole’s head is monitored by a speed transducer in accordance with the excitement frequency.
Knowing the applied force’s value it is possible to trace back to the mechanical admittance (ratio between the speed at the pole’s head and the applied force), a magnitude directly related to the vibrational behavior of the pole-soil complex. This feature allow to establish the pole’s geometry (lenght,section variations), through some elaborations and analysis of the curve admittance-frequency.
This test provides the installation of appropriate accelerometers connected to shared or separated acquisition circuits; this acquisition system could in turn be connected via telephone modem to the Geo-Consult Data Processing Center.
The execution of such tests needs preparation of the pole’s head at least 24 hours before the test, in order to level and make more uniform the surface where the vibrator will be fixed.