Analytical Method And Numerical Simulation Of Interal Force And Deformation Of Torsional Single Pile By Enegy Principle

Due to the advantages of high bearing capacity, small settlement, convenient construction and applicability in complex geological environment, pile foundations are widely used in foundation engineering. In addition to the conventional vertical loads, the piles used in cross-sea bridge, the city overpass, offshore drilling platforms or wind turbine tower and other stuctures,will encounter considerable torque as a result of the uneven or eccentric horizontal force, the side impact loads or seismic force at the top. In general, the existed conventional design methods do not consider the influence of torque. However, that the presence of torque accelerates the destruction of the pile foundations, will makes it difficult to evaluate the bearing capacity of the pile reasonably, and sometimes even makes the design unsafe and endanger the upperstructure. In this context, combined with National Natural Science Foundation of China（51378197）, theoretical analysis and numerical simulation study on the torsional pile foundations in the more realistic model of foundation are conducted based on existed research and achievements, the main work is as follows:Firstly,the subsoil modulus profile is taken as a power law variation of depth with a nonzero value at the surface（usually treated as zero）,the virtual pile is introduced to establish the total energy function of pile-soil system,from which the differential government equations for the pile shaft and subsoil is derived by the principle of minimum potential energy and variational methods respectively.Then the finite difference method is adopted to obtain the differential equation of twist angle along the pile shaft.Regarding the subsoil as elastic-perfectly plastic material,a torsional analysis method of single pile under plastic bearing status with a program developed by the MATLAB software as well.The proposed method is verified by comparing the results with that by other available methods and model tests.Finally, a parameter analysis is carried out to find out the influencing rules by the pile parameter G_p and r₀ as well as the soil parameter a_g and n on the torsional response of pile shaft.Secondly,the torsional pile analysis method in single layer of soil is extended to more complex multi-layered soil,the subsoil modulus profile of multilayer soil is still taken as a power law variation of depth with a nonzero value at the surface,the energy equation of pile soil system in two-layer soil is established,and get the twisted equations,then the finite difference method is adopted to obtain the differential equation of twist angle Then, the inner forces（torque T） and deformation（torsion angleφ） at the pile top and along the pile shaft is obtained respectively by solving the equation.Finally, with the aid of ABAQUS software, pile calculation model is established. Then the results of numerical analysis is compared to the calculation of energy method and test values of existed model test,and inner force and deformation analysis method of torsional piles based on energy principle is verified.