Study On Drivability During Pile Redriving In Ocean Engineering

Pile driving in off-shore platform foundation is a comprehensive and systematic study involves many subjects as dynamics, structure mechanics and soil mechanics. Owing to the special oceanic circumstances, the pile could not continuously drive to the design penetration; finally there emerges the situation of the driving refusal in the process of construction. After the interval stop the driving continues and that is called pile restart. In the process of pile restart, as the strength of soil body enhanced, the resistance appears more and more obvious; finally it refuses the pile driving. In such situation the traditional method is time-consuming and money-wasting. So it is important to make a further research into these problems.This research focused on the reasons of driving refusal and its settlements, based on the cavity expansion theory and the dynamic consolidationthen theory, the change of soil behavior during continual driving was analysed. Then we concluded that it was because of the restoration and even the enhancement of the soil strength after pile driving as the water pressure of excess pore reduced with the time gradually went by. In order to calculate how much soil strength increased, studing on the program of analysis driving pile TNO, which based on the wave theory, some important parameters were analyszed and the program was applied to practical project. Wave theory took the process of pile driving as the transmitting of the stress wave in the pile, because this kind of theory agreed well with the reality, it made a good predicted result.Through analysis, this research gave an available method—a back analysis method to deal with the refusal of pile driving. It referred to the program of analysis driving pile TNO, which made use of the records of pipe driving, and based on the theory of dynamic consolidation and cavity expansion, then deduced the bearing capacity of a single pile. If the bearing capacity satisfied the demand, it is considered that the pile foundation reached the demand and there was no need to driving any more. This method has been already used in real project, and made good consequences.