Bearing Capacity Analysis Of A Single Pile Under V-H-T Combined Loading In Sand

With the rapid development of China's economy,the demand for offshore resources development is becoming more and more urgent.Coastal engineering,such as offshore generating units and offshore drilling platforms,is constantly emerging.Due to its advantages such as high bearing capacity,strong stability and mature construction technology,pile foundations have been widely used in coastal engineering projects.This type of pile foundation is not only large in size,but also subjects to complex and variable force condition.However,the traditional design theory of pile foundation based on small deformation principle has great limitations.It is of great practical significance to study the bearing and deformation mechanism of pile foundation under the combined action of vertical force(V),horizontal force(H),bending moment(M)and torsion(T).Based on the existing research results,the bearing characteristics of V-H-T combined loaded piles are discussed by test analysis,theoretical calculation and numerical simulation.The main work are as follows:Firstly,the deformation law and failure mode of pile under single vertical,horizontal and torsional loads are summarized.Based on the modified ? method,the shear displacement method and the improved finite element method,the bearing mechanism of pile under the combined action of V-H,V-T and H-T loads is analyzed in turn,which provides theoretical basis for indoor model test and numerical simulation.Secondly,a series of indoor single-pile model tests were carried out in homogeneous sand by self-developed test loading system.The ultimate bearing capacity of pile body,internal force displacement,the deformation curve of pile body under combined V-H-T loads and failure modes under various working conditions were obtained.The failure mechanism of pile body is discussed and the interac tion rule of three loads on the bearing capacity of pile body is analyzed.Furthermore,the bearing capacity envelopes of V-H-T combined bearing pile are obtained.And the simplified calculation formula of bearing capacity of pile body is obtain ed by dimensionless treatment and fitting for engineering design reference.Then,based on ABAQUS platform,the numerical analysis model of single pile under V-H-T combined loads is established.The envelopes of bearing capacity of pile under V-H,V-T and H-T different load combinations are obtained by probe loading method.The three-dimensional envelope of bearing capacity under V-H-T combined load is obtained by load-displacement joint search method.According to the load combination value(V,H,T)of pile foundation in practical engineering,the safety of pile foundation can be judged.Finally,the application analysis is carried out with the static load test of a project.By comparing the results of model test and numerical simulation with the measured load-displacement data,the bearing characteristics of the pile under combined load are further discussed.