考虑异形效应Y形桩侧摩阻力产生附加应力研究

RESEARCH ON ADDITIONAL STRESS CAUSED BY SKIN FRICTION OF Y-SECTION PILE CONSIDERING ABNORMALITY EFFECT

Y形桩作为一种新型反拱曲面异形桩,侧土压力和侧摩阻力具有沿桩周不均匀分布的特性,虽将侧摩阻力假定为均匀分布与假定为集中力相比,附加应力计算结果更符合实际分布规律,但仍存在一定偏差。基于球形孔扩张理论,建立了Y形桩桩侧侧土压力的不均匀分布模型,进而建立了侧摩阻力的不均匀分布模型,并用于附加应力的计算。以主要影响因素外包圆半径R、模板弧度θ为变量,分别对比研究了将Y形桩侧摩阻力假定为集中分布、均匀分布和考虑异形效应不均匀分布三种模式下附加应力的变化规律,并将考虑异形效应的侧摩阻力产生附加应力计算方法用于沉降计算,通过现场静载荷试验数据验证,考虑异形效应的侧摩阻力产生附加应力计算方法所计算的沉降值与实测值吻合度更高。

Y-section pile is a newly abnormal pile with reversed-arch surface. The lateral earth pressure and skin friction surrounding the pile shaft are of non-uniform distribution. Although the calculated results of additional stress caused by assumed uniformly distributed skin friction are more suitable to the actual distribution law when compared with those caused by the assumed concentrated skin friction, there is still a certain error. Based on spherical cavity expansion theory, non-uniform distribution model of lateral soil pressure around Y-section pile is established; and then the non-uniform distribution model of skin friction is built up as well, which can be used to calculate the additional stress. Taking outside circle radius R and template radian 0 as variables, variation laws of additional stress are comparatively studied under three distributed patterns of skin friction around Y-section pile respectively, namely the concentrated distribution, the uniform distribution, and the non-uniform distribution considering the abnormality effect. In addition, the calculated method of additional stress due to skin friction is employed to calculate the settlement by considering abnormality effect. According to the field static load tests, it was found that the calculated settlements agree better with the measured results using the calculation method of additional stress due to skin friction by considering abnormality effect.