Dynamics and Monitoring of Vibratory Piling Process

The foundations of buildings in urban environments are very often piled ones. During earth moving works the sides of digging area have to be supported by sheet pile walls to maintain constant earth pressure conditions against existing foundations. The piles and sheet piles are very often driven by vibratory methods, in which case the ground vibration is a risk for neighboring old buildings. The purpose of the present research work is to find a new, theoretically well established way to use vibratory pile drivers environmentally friendly especially in urban environments. Closely related to this a new electro-hydraulic circuit has been introduced by Unisto company for on-line adjusting of the phase angle between primary and secondary shafts of eccentric masses in the vibratory unit. Furthermore, the control of this angle will be subjected to continuous monitoring from the vibration level of the critical structure to be protected. The control of shafts phase angle is based on separate drive technology, in which the position difference is governed by electrically controlled orifices. Vibration control principle is based on the requirement to stay below required vibration bounds in the working environment. The system is equipped with a vibration sensing box to be fixed on to the protected structure, from which the vibration level information is transmitted to the control box of vibratory unit. The described system is investigated both theoretically and numerically. The theoretical part of the research includes the derivation of complete system equations. In the numerical part of the work the system is coded and simulated by computer to get required information for system modifications and dimensioning. The main objective of these research steps is to evaluate the operation of phase angle adjusting system in order to balance the control of environmental vibrations and machine performance.