中文摘要：

为探讨桩顶竖向力（V）和扭矩（T）共同作用时的桩身受力特性,于桩顶先作用V后施加T,视桩周土为Gibson地基,并考虑桩-土接触面上的位移非协调性,基于剪切位移法和桩身荷载传递函数建立出桩身位移控制方程,引入力和位移边界条件后,推导出桩周土处于不同受力阶段时的桩身内力位移解析解,由此求得不同V-T组合作用下的桩身承载力,进而获得桩身承载力包络图。进一步的参数分析表明,对于V-T联合受荷桩：保持桩身长径比m0不变,桩身承载力随桩长L的增加而变大,而L不变时,桩身承载力随m0增加而增加;随桩土刚度比λ、桩侧土体剪切模量和极限摩阻力分布常数比值n的增大,桩身承载力逐渐减小;随桩顶扭矩的增加,桩顶所能承受的竖向力不断减小,且减幅先快后慢,最终趋于零。

英文摘要：

In order to discuss the behavior of piles under combined loading of vertical force V and torsion T, the paper firstly set up the governing equation of the pile shaft using the shear displacement method and pile shaft load transferring function, in which the subsoil was treated as the Gibson model and the non-coordination deformation along the pile-soil surface was considered as well. Then, both the force and displacement boundary conditions were introduced to solve the equation, generating the analytical solutions of internal forces and deformations for the pile shaft under various bearing stages of subsoil. Based on the solutions, various combined loadings of V and T were considered to determine the bearing capacity of the pile shaft, from which a V-T combined loading envelop was plotted correspondingly. The parameter analysis results show that the bearing capacity of piles under V-T combined loading increases with the pile length （L） when the aspect ratio of pile shaft （mo） is kept constant. For a constant L, the bearing capacity of pile shaft increases with the increasing value of m0. Furthermore, the bearing capacity of the pile shaft becomes larger as a result of increasing the stiffness ratio （λ） of pile shaft to surrounding subsoil, and／or increasing the ratio of the constant coefficient of the subsoil shear modulus distribution function to that in the ultimate friction resistance distribution function （n）. The vertical force capacity of pile decreases as the torsion at the pile top increases gradually, and the drop in vertical force capacity becomes less significant with the increasing of the torsion.