Bearing Behavior Of A Single Pile Under Combined Loading Of H-T By Model Test And Numerical Analysis

In recent years,with the continuous development of offshore resources,the scale of offshore platforms,wind power towers,etc.are being expanded unceasingly.Due to its advantages in high bearing capacity,low costand convenient constructions,pile foundations are widely used in engineering practice.the pile Foundation is widely used in this kind of engineering,and the pile foundation not only bears the function of horizontal force,vertical force and bending moment,but also often bears not negligible torque.When the weight of superstructure is relatively small(such as wind power tower),horizontal H and torque T become the control factor of pile bearing capacity.The simple superposition principle may cause the design to be biased to unsafe and lead to catastrophic consequence.For these reasons,based on the relevant research work,indoor model tests and numerical simulation analysis combined with the relevant theory were adopted to discusse the bearing characteristics of single pile foundation under different values and loading sequences of combined horizontal force H and torque T.The main work is as follows:Firstly,the distribution regularity of internal forces and deformation for a single horizontal loaded pile and a pure twisted pile were summarized.And the bearing characteristics of single pile under combined loads of H-T based on the improved finite element method was discussed in detail,which provides the basis for the indoor model tests and numerical analysis.Secondly,the self-developed combination loading devices were used to carry out a series of single-pile static load test under the combined loads of H,T and H-T in homogeneous sand,from which the values and distribution regularity of internal forces and deformation along the pile shaft were obtaied with ultimate bearing capacity determined as well.Furthermore,the bearing and failure mechanism of pile shaft as well as the influence of different loading order on the bearing capacity of the pile were analyzed,respectively.And the interaction curves of bearing behavior(i.e.,the bearing envelopes)of the pile shaft under combined loads of H-T were drawn,from which a simplified formula to calculate the bearing capacity of single piles under combined loads of H-T was given for engineering application.Finally,based on ABAQUS,the three-dimensional numerical analysis model of single pile foundation in homogeneous sand was established,and the resules of numerical simulation analysis were validated with the existed results of the theoretical and experimental research model test under the single-level loaded piles and pure twisted piles.The stress and displacement cloud of the pile body and soil surrounding pile are obtained under the combined loads of H-T by numerical simulation analysis,and the piles bearing deformation characteristics under combined loads of H-T are discussed.On these basis,obtained the influence regularity of the internal force deformation of pile by the parameters of pile and soil material like the Elastic Modulus Ep(Es),Poisson's ratio vp(vs),piles-soil friction coefficient ?and pile length diameter ratio,load order of pile cap under the combined loads of H-T by parametric analysis.At the same time,the calculated results of the pile body torque under the combined loads of 1/2Tu?Hu are compared and analyzed with the improved finite element method and model test.