On the loss of contact between driving element and soil during vibratory driving into saturated soil

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Vibratory pile driving is a proven method of driving piles into the ground quickly and economically. Compared to other methods, vibratory pile driving represents a relatively low-vibration and low-noise method of driving piles. Current investigations show insufficient agreement with the observations and interpretations of colleague Cudmani. During upward movement, a cavity may form under the pile toe. The nature of this presumably developing cavity is not fully understood. Besides, the separation between pore water and soil particles and a possible phase transition of the pore water to water vapour (cavitation) due to negative pressure has not been adequately explored. The cavitation pressure required for this is achieved when the pore water cannot flow into the cavity sufficiently quickly due to the permeability of the soil. The main objective of the research project is therefore to clarify the processes at the base of the profile during the upward movement of the vibrated pile and determine the effect of the driving process on the static load-bearing behaviour. Another objective is to investigate the influence of physical cavitation and the presumed cavity under the pile toe during vibratory driving. For this purpose, numerical simulations are carried out, which are supplemented and validated by model tests.