Discrete Element Modelling Of Mechanisms Of High Frequency Hydraulic Vibratory Pile Driving

As the technique of high frequency hydraulic vibratory pile driving has manyadvantage such as low noise, powerful penetrability, widely adaptation scope，smalldamage to pile shaft etc., It is widely used in the domestic and foreign actual projects.However, especially in the domestic, the relevant research actually by far falls behind thepractical application. The process of high frequency hydraulic vibratory pile driving is verycomplex，involves many other difficult problems such as the soil behaviour under cyclicshear, partial liquefied and strength degradation,the interaction between pile and soilduring high frequency vibratory driving and so on. The past studies mainly focus onnon-cohesive soil, and they did not take account of the influence of the excess pore waterpressure.Base on the above background, the thesis fully takes advantage of the PFC3Dprocedure can well simulating the partice motion, analyze the issure of drivability of highfrequency hydraulic vibratory in cohensive soil from macro and micro aspects, the contentsas below:Firstly, the mechanisms of high frequency hydraulic vibratory pile driving areelaborated, and the past research work are summarized including experimental studies,theorial studies and numerial analyse, the development and application of the discreteelement are also summarized at the same time.Secondly, the relevant basic principles and methods of discrete element areintroduced in detail. It is validated that the coupled continum-discrete procedureDEM-CFD can effectively take accounting of the influence of pore water pressure throughmodelling the compression and consolidation in one dimension by discrete elementmethod.Thirdly, the whole process of high frequency hydraulic vibratory pile driving ismodelled by discrete element method, the changes of soil behaviour during the processincluding the particle motion trace, porosity, cantact force and pore water pressure areanalyzed, conclude the law of the shaft and toe resistance changes,.The effect factors such as vibratory frequency,static loads, exciting force,the diameter of pile,the modulus ofsoil,the friction angle of soil ect.on penetration speed and depth are revealed.the effect ofpore water pressure is also discussed by comparing saturated clay to dry clay.Finally, the drivability of large diameter long pile is modelled, the numeric results ofthe whole penetration are revealed through a exmaple, and some correspondingly analyseare discribed.