非均质地基中V-T联合受荷桩承载力分析

Bearing Capacity Analysis of Piles under V-T Combined Loading in Non-homogeneous Soil

为探讨非均质地基中V-T联合受荷桩的承载特性,考虑地面处桩周土体剪切模量为非零值且随深度呈幂函数分布,计入桩-土接触面处位移非协调性及加载顺序的影响,基于剪切位移法和桩身荷载传递函数建立桩身位移控制方程,并引入相应力和位移边界条件,导出桩周土体在不同受力状态下桩身的内力位移解析解,进而推导出不同加载顺序下V-T联合受荷桩的承载力,从而得到其承载力包络图。V-T联合受荷桩参数分析结果表明:桩身承载力随长径比L/D增大而增大,而随桩侧土体剪切模量与极限摩阻力分布常数比n、桩土弹性模量比λ增大而减小;桩顶所受扭矩T不断增大时,其能承受的竖向力V随之变小并最终趋于零,且T→V承载力包络线始终处于V→T承载力包络线内侧。

To discuss the behavior of piles in non-homogeneous soil （the soil shear modulus profile follows power law with depth） under combined loading of vertical force V and torsion T, the control equation of the pile shaft was first set up based on the pile shear displacement method and shaft load transferring function, in which the non-zero shear modulus at the ground surface and the non-coordination deformation along the pile-soil interface and various loading sequence were considered as well. Then, force and displacement boundary conditions were introduced to deduce the analytical solutions for the internal force and deformation of the pile shaft under various bear- ing stages of subsoil, from which the bearing capacity of the pile shaft were calculated and the failure envelops were plotted under various loading sequence. Parameter analysis shows that, for V-T combined loaded piles, the bearing capacity will increase with the increasing of aspect ratio L/D, whereas decrease with the increasing of the constant ratio between the subsoil shear modulus and the ultimate friction resistance （n）, and the stiffness ratio （λ） between pile shaft and sub- soil. Increasing the torsion at the top of pile will result in a decreasing vertical bearing capacity with a final zero value. Besides, the failure envelop under T-→V loading sequence remains inside of that under V→T loading sequence.