螺纹桩承载机理及承载力计算方法

THE BEARING MECHANISM AND CALCULATION METHOD OF BEARING CAPACITY OF SCREW PILE

螺纹桩是一种全新的带螺牙的混凝土灌注桩。根据理论分析和试验研究,当螺纹桩螺牙间距较小时,受力时螺牙带动周围土一起移动,类似多节扩孔桩受力;当螺纹桩承载力达到极限时,桩身沿螺牙外侧的圆柱面破坏,承载力为桩侧提供的承载力及桩端阻力。通过整理目前螺纹桩承载力的几种计算公式,对几种它们的优、缺点进行分析。为方便设计计算,在传统直杆桩承载力计算方法基础上提出了一种螺纹桩承载力计算新的方法,对计算方法中螺纹桩等效侧阻较干作业钻孔桩侧阻的增强系数进行了理论分析,最后结合实际工程进行统计分析,并提出工程设计中增强系数的经验取值。

The screw pile is a new kind of casting concrete pile which is of screw pitch on pile body.According to theoretical analysis and testing research,if the screw pitch is short,when loaded,screw thread moves with soil around it,similar to multistage expanding pile.When the bearing capacity of screw pile reaches to the ultimate load,it will be broken through the cylndrical surface out of pile,and the bearing capacity is sum of shear resistance between soil and screw threads and end resistance.Several calculation methods of bearing capacity of screw pile were introduced and also the merits and demerits of the calculation methods were analyzed too.In order to supply simple and convenient calculating method,based on the traditional calculation method,a new calculation method of screw pile bearing capacity was proposed and the factor of equivalent shaft resistance on screw piles to shaft resistance of bored pile in dry operation was analyzed and calculated theoretically,the calculating factor was put forward for engineering design.