Bearing Capacity Characteristics Analysis Of Single Pile Under V-T Combined Loading In Double-layered Subsoil

In recent years,with the advancement of infrastructure construction in our country,as the pile foundation has the advantages of high bearing capacity,small settlement and convenient constructions,therefore it is often used in engineering practice especially adopted in the offshore resources,the construction of overpass and bridges over large rivers or ocean.But this kind of structure is usually working in a complex environment,therefore,besides the vertical loads V down from the superstructures,obvious torsinal load T are often caused at the pile top by non-uniform or eccentric horizontal forces,this results in a complex pile bearing deformation state.Those conventional design methods can not consider this kind of interaction between the vertical load V and torsion T,making it difficult to accurately evaluate the bearing capacity of the pile shaft,sometimes even result in the insecurity of upper structures.Thus,based on the existing research results and supported by the National Natural Science Foundation of China?NO.51378197;NO.51578231?,this study investigated the bearing behavior and deformation mechanism of single pile under V-T combined loading in double-layered subsoil by theoretical analysis and numerical simulation.The main works are as below:?1?Considering the shear modulus and the limit friction resistance of each soil layer was assumed as an increasing distribution with the depth defined by a power function.Then,considering various loading sequences and the non-coordination deformation along the pile-soil interface,the control equation of the pile shaft was first set up by the load transferring function and shear displacement method.Subsequently,analytical solutions were deduced to calculate the inner forces and deformation of the pile.Above solution degradation to the single homogeneous foundation,heterogeneous foundation as well as the upper and lower homogeneous double-layered foundation,again with the previous theoretical resu lts are verified,and the correctness of the solutions presented in this paper.?2?Based on the solution of single loaded pile,subsequently,analytical solutions were deduced to calculate the inner forces and deformation of the pile shaft under various bearing stages and loading sequences?V?T or T?V?.Then,the Mathcad calculation program was programmed to analyze the parameters.such as the slenderness ratio of pile shaft?L/D?,loading sequences and constant coefficients determining the subsoil shear modulus distribution?m₁,m₂,n?.?3?Based on the ABAQUS finite element software platform,a series of 3D numerical models for a single pile under vertical and torsional combined loads in two-layered nonhomogeneous soil.By comparing the results from the numerical models with available achievements,the accuracy of the models was verified.Finally,a parameter analysis was carried out to discuss the influencing laws by the key factors such as the slenderness ratio of pile shaft?L/D?,loading sequences,constant coefficients determining the subsoil shear modulus distribution n,non-homogeneity coefficient?and loading method.