Driving And Pulling Mechanisms Of The Sleeve Of Large Diameter Benote Pile By High Frequency Vibratory

The settling sleeve cast-in-place piles,which driving and pulling sleeve by high frequency vibration hydraulic hammer usually called Benote pile,with the advantages of low vibration sense and noise,and high efficiency.For some areas,which are sensitive to vibration and noise,this method provides a good solution for pile foundation construction.To better popularize this method in practical engineering,the change of soil behaviors and impact on the surroundings caused by using high frequency vibration hammer to drive and pull sleeve is necessary.In this paper,two three-dimensional numerical models by ABAQUS,including driving sleeve and pulling sleeve model,are used to investigate the effects and mechanisms of sleeve driving and pulling on surrounding soils.To save computational resources,adopt 1/4 model to simulate.It can’t be ignored that the soil large deformation caused by sleeve driving and pulling,and then the mesh distortion phenomenon,due to large deformation,is a great challenge for finite element calculation.For the above problem,arbitrary Lagrangian eulerian(ALE)method is an ideal solution.Besides,the Finite-element and Infinite-element Coupling model is used to eliminate the effects of boundary reflection of vibration wave.The constitutive model of Mohr-Coulomb is adopted to imitate the soft clay,and undrained strength indexs are applied in this analyse.The near and far field soil are simulated with C3D8R element and CIN3D8 element respectively.The high frequency vibration load refer to ICE815C vibration hammer,and the frequency assumes 27 Hz.In this paper,introduces the principle of the arbitrary Lagrangian eulerian method firstly,as well as the key points of ABAQUS modeling,including the constitutive model,sleeve driving and pulling method,the finite element-infinite element coupling principle,the principle of contact problem,the selection of important parameters,the high frequency vibration load and pore water pressure calculation method,etc.Sleeve driving:first,compare different element(including Hex,Wedge and Tet element)impact on the calculation and select the most ideal element to model.Through the field measurement data and empirical formula to verify driving model,judge the accuracy and rationality of model.Then,analyse the changes of sleeve driving velocity and soil behaviors,such as displacement,stress(including excess pore pressure),velocity and the soil plug,to conclude the mechanism of the soil properties changes during the sleeve driving.Finally,through the analysis of soil parameter(including soil young’s modulus and soil-sleeve friction coefficient)and vibration hammer parameters(such as vibration frequency)to explore influence of parameters on sleeve driving caused by parametric variation.Sleeve pulling:first of all,an analysis about sleeve pillability is drawn,computing the minimum sleeve pulling force to determine the parameters for the high frequency vibration hammer.Among them,the casing cast-in-place concrete pile with silt soft soil instead.Then the in-situ measured data to verify this model,judge the accuracy and rationality of sleeve pulling model.After,analyse the changes of sleeve pulling velocity and soil behaviors,such as displacement,stress(including excess pore pressure),void ratio and velocity,to conclude the mechanism of the soil properties changes during the sleeve pulling.Finally,through the analysis of soil parameter(including soil young’s modulus and soil-sleeve friction coefficient)and vibration hammer parameters(such as vibration frequency and vibration force)to explore influence of parameters on sleeve pulling caused by parametric variation.