To investigate the bearing behavior of a single pile in uniform sand under the combined action of horizontal harmonic load H(t) and torque T

the modified finite bar element method is used to establish the comprehensive stiffness matrix of the pile shaft with consideration of the stiffness contributed by the surrounding subsoil and the coupling effect between H(t) and T. Then

the internal forces and deformations of H(t)-T combined loaded pile are solved by MATLAB

and a detailed parametric analysis is carried out to discuss the influence of length-diameter ratio (L/D)

pile-soil stiffness ratio (Ep /Es)

dimensionless frequency (a0) and amplitude (Q0) of the horizontal harmonic load

and boundary conditions of the pile toe on the bearing behavior of pile shaft. The results show that as the depth of the pile increases

the bending moment along the pile shaft first increases and then decreases sharply

while the torque and deformation reduce drastically to almost zero in the end

i.e.

there is an effective pile length ld. The ld

internal forces and displacements are greatly affected by Ep /Es. When Ep /Es increases from 1 500 to 3 500

ld rises from 27.3D to 44.1D

and the maximum bending moment of the pile increases by 23.5%

but the horizontal displacement and torsional angle at the ground surface decrease by 19.0% and 26.0%

respectively. Decreasing a0 or increasing Q0 can relatively improve the torsional bearing capacity of the pile shaft. The boundary conditions of the pile toe only affect the internal forces and deformations of finite-length piles.