挤土作用下Y型桩侧摩阻力分布模型研究

Y型沉管灌注桩是在传统圆形桩基础上通过改变截面形状以增大桩土接触面积、增加侧摩阻力进而增加承载力的一种新桩型。由于桩身截面的特殊性，在振动沉管的过程中Y型沉管灌注桩截面不同处对土有不同程度的挤压作用，其侧摩阻力分布性状比圆形桩复杂，若将Y型桩侧摩阻力看作沿桩身矩形分布、沿桩周均匀分布与实际不符，工程经验亦表明其不适。通过孔扩张理论与Y型截面的解析方程相结合，推导Y型桩侧摩阻力沿桩周及桩身的不均匀分布模型，同一截面最大侧摩阻力为最小侧摩阻力的1.24~1.75倍，同时分析外包圆半径R、模板弧度θ、桩长L对侧摩阻力的影响。将侧摩阻力沿Y型截面周边的9个区间积分，然后沿桩长积分，得到Y型桩总侧摩阻力，结合端阻力模型计算了Y型桩单桩极限承载力，与静载试验数据吻合。

Research on skin friction distribution model of Y-shaped vibro-pile under soil-compacting effect

Y-shaped vibro-pile is a new type of pile, compared with the traditional circular pile, the Y-shaped cross-section pile increases the contact area of the pile and soil, and thus increase skin friction and the bearing capacity. Due to the particularity of the pile cross-section, when Y-shaped pile is driven by pipe with vibration, different area of Y-shaped section have varying degrees of compression on the soil and its skin friction distribution trait is complicated than circular pile. Simplifying Y-shaped pile skin friction as rectangularly distributed along the pile length direction and uniformly distributed along the section perimeter direction does not match with the actual and the engineering experience also shows its inappropriate. Firstly, combining the cavity expansion theory and the analytical equations of Y-shaped section to deduce the nonuniform distribution, it is shown that the maximum skin friction is 1.24-1.75 times larger than the minimum skin friction at the same cross-section; the influences of three variables R, θ, L of Y-shaped pile on skin friction are also analysed. The total skin friction can be calculated by quadraturing the skin friction along nine integral regions of the Y-shaped section and the pile length direction，combined with the tip resistance，the ultimate bearing capability is obtained and consistent with the data of static loading test.