Study On Longitudinal Vibration Of Large Diameter Piles In Heterogeneous Saturated Soil

In this paper,vertical vibration characteristics of large diameter piles in bi-directional heterogeneous saturated soil are analyzed according to three aspects of theory,numerical simulation and test.Through the establishment of the pile dynamic response equation,the vertical vibration characteristics of diffused fictitious soil pile model of large diameter piles and large diameter socketed piles are analyzed under the influences of water volume fraction,dry or saturated soil,longitudinal soft and hard intercalation and construction disturbance degree of pile side soil,thickness of pile bottom sediment.By the aid of numerical simulation and indoor experiment,the correctness of the theoretical modeling and its solutions are verified on one hand,on the other hand,the feasibility of the numerical simulation method and the experimental method are verified by the analytical model in theory,in turn.This paper is mainly analyzed from the following aspects:(1)Considering the bidirectional heterogeneity of the soil around the pile,based on the plane strain model of complex stiffness transmission,according to the dynamic response equation of saturated soil and the longitudinal vibration equation of large diameter pile,the dynamic response equation of pile top is obtained.The vertical vibration characteristics of diffused fictitious soil pile model of large diameter piles are analyzed under the influences of water volume fraction,longitudinal soft and hard intercalation and construction disturbance degree of bi-directional heterogeneous saturated soil around pile.The study shows that the bi-directional heterogeneity of soil has an obvious influence on the dynamic response of the pile-soil based on the diffusive soil pile model.(2)Considering the bidirectional heterogeneity of the soil around the pile,based on the plane strain model of complex stiffness transmission,according to the dynamic response equation of saturated soil and the longitudinal vibration equation of large diameter socketed pile,the dynamic response equation of pile top is obtained.The vertical vibration characteristics of diffused fictitious soil pile model of large diameter socketed piles are analyzed under the influences of water volume fraction,longitudinal soft and hard intercalation and construction disturbance degree of bi-directional heterogeneous saturated soil around pile,thickness of pile bottom sediment.The study shows that the bi-directional heterogeneity of soil has an obvious influence on the dynamic response of socketed pile.(3)Building the coupling vibration model of large diameter pile-soil based on diffused fictitious soil pile model and large diameter socketed pile-soil model with ansys to analyze influences of water volume fraction,longitudinal soft and hard intercalation and construction disturbance degree of bi-directional heterogeneous saturated soil around pile and so on.The solutions are compared with theoretical solutions to verify the correctness of the theoretical solutions and the feasibility of the method of numerical simulation.(4)The concrete piles with different diameters are tested with pile foundation detector to get the velocity response curves of pile head.The curves are compared with theoretical curves to verify the correctness of the theoretical solutions and the feasibility of the experimental method.