斜桩负摩擦及弯曲特性研究

针对软土地区设计桩基础遇到的最普遍问题——负摩擦,通过三维数值模拟研究斜桩在超载作用下的负摩擦和下拉力特性。指出由于桩身倾斜,超载不仅引起桩身负摩擦,还产生附加弯矩。参数分析结果表明:随着桩身倾斜角度的增加可减小桩身负摩擦力和下拉力,桩顶约束时在桩身中部产生较大的弯矩,而桩顶自由时则在桩身下部产生弯矩;桩身下拉力及负摩擦力的变化主要取决于地面超载和轴向荷载,在桩顶施加轴向荷载之前先加超载比先施加轴向荷载后再加超载可大幅度减少桩身负摩擦。

Study on negative skin friction and flexural behavior of batter pile

Negative skin friction is perhaps one of the most common problems in the design of pile foundations in soft soils.Three-dimensional elasto-plastic numerical analyses were carried out to evaluate the development of negative skin friction and drag load for a single batter pile subjected to surcharge,which not only causes the negative skin friction but also causes increased bending moments due to the shaft incline.The parametric analyses show that negative skin friction and drag loads for single piles are reduced by the increase of the batter angle.The condition of fixed-head piles will cause higher bending moments in the middle part,while the condition of free-head piles will cause higher bending moments at the pile base.Drag load development heavily depends on the surface surcharge and axial load.When the surcharge precedes the application of the foundation working load,the effect of negative skin friction is considerably smaller than in the reverse case.