印尼某电站基桩的负摩阻力及其措施

Negative Skin Friction of Foundation Pile and Countermeasure at A Power Station in Indonesia

基于印尼某电站场地的工程地质条件,根据基桩负摩阻力的产生机理,分析确定了中性点的位置,计算了负摩阻力产生的下拉荷载;并结合膨润土泥浆护壁的作用机理,计算了采取较大直径预钻孔和膨润土泥浆护壁的措施后负摩阻力产生的下拉荷载。计算结果表明,前者大干单桩承载力设计值,因此不能采用预应力混凝土管桩方案;后者较前者显著降低,约为单桩承载力设计值的50%,因此可以采用预应力混凝土管桩方案。

Based on the engineering geology condition of the power station in Indonesia and the forming mechanism of negative skin friction,the neutral point for skin friction of foundation pile is analyzed and established. The pull-down force is reproduced by negative skin friction and countermeasure is adopted to reduce the negative skin friction. According to the reciprocal-action mechanism between bentonite slurry and soil,the pull-down force is calculated and the countermeasure is adopted by means of pre-borehole and protecting borehole wall. The pre-borehole diameter is big than the pile and the borehole wall is protected by bentonite slurry. It is showed that the former is more than the designed bearing capacity of single pile with a dissatisfactory result using precast concrete spun pile,and the latter is approximatly a half of the designed bearing capacity of single pile with a satisfactory result using the precast concrete spun pile.