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

With the continuous development of infrastructure construction in China,especially the continuous development of offshore resources,the city of three-dimensional traffic curved bridge,sea bridge,offshore wind power tower and other structures continue to build.In order to meet the requirement of the bearing capacity,deformation and stability of the superstructure,the structure is mostly based on the pile foundation,but because of its complicated environment,besides the vertical force(V),the horizontal force(H)And bending moment(M),the torque(T)can not be ignored.Conventional design methods are difficult to consider this complex load conditions,can not evaluate the ultimate bearing capacity of the pile reasonably,causing the design to be biased towards insecurity.Therefore,the combined effects of V,H,M or T should be taken into account for the design of pile foundations in such complex stress environments.Therefore,based on available research work and achievements,theoretical analysis and numerical simulation of the bearing capacity of single pile foundation under different combinations of V,H,M and T loads in non-homogeneous subsoil are carried out.The main work is as follows:Firstly,to discuss the bearing behavior of a single pile under combined loading of vertical force V and torsion T in non-homogeneous subsoil,the control equation of the pile shaft was first set up by using the pile shaft load transferring function and shear displacement method,in which the exponential function model was adopted to simulate the increasing change of subsoil shear modulus and ultimate side resistance with depth,and the non-coordination deformation along the pile-soil interface was considered as well.Then,force and displacement boundary conditions were introduced to deduce the analytical solutions for the inner forces and deformation of the pile shaft under ideal elastic-plastic bearing stages of subsoil.Based on the obtained solutions,various combined values and loading sequences of V and T at the pile top were adopted to determine the bearing capacity of the pile shaft,from which failure envelops were plotted correspondingly.Secondly,based on ABAQUS,a three-dimensional numerical analysis model of bearing capacity of single pile foundation in non-homogeneous subsoil is established.The numerical simulation of pile under single vertical load?horizontal force and torsion as well as V-T and H-M-T load conditions are carried out respectively.Compared with the existing results,the reliability of the model is verified,which provides the basis for further analysis of the bearing capacity of the combined load.Thirdly,based on the three-dimensional numerical model of bearing capacity of single pile in non-homogeneous subsoil,the bearing characteristics of single pile under different combinations of V-H,V-T,H-T,V-M,V-H-M and V-H-M-T are analyzed respectively and discussed the influencing rules by the aspect ratio(L/D),elasticity modulus ratio(?)of pile shaft to subsoil.Then,the envelope of the pile bearing capacity under different load combinations and loading sequences is obtained,and the damage mechanism of the pile body is discussed according to the displacement vector diagram under the corresponding failure state.Finally,a comparative analysis was performed to find out a good agreement between the theoretical calculation results and results of test pile in a project instance.