碰撞力学原理在动力打桩过程分析中的应用

Application of collision mechanics in dynamic pile driving process analysis

以"能量守恒"为基础分析动力打桩过程中最后贯入度极限承载能力预估分析法的海利公式,被得到广泛应用和认可,但公式中系数取值是复杂而困难的过程。事实上动力打桩过程就是利用桩锤的锤芯与桩顶碰撞过程中产生的巨大瞬时力进行沉桩。碰撞过程中力的变化十分剧烈,并伴有强烈的声、光、热等机械能损失。文章以基础物理学的碰撞原理,应用"动量守恒"定律,将锤与桩作为一个体系,建立起锤击位移与运动速度之间的关联,推导出了锤击力的估算公式。为动力打桩选锤,桩基极限承载能力估算提供了一种新的方法。

On the basis of"conservation of energy",the Haley formula,which is used to analyze the ultimate load bearing capacity of final penetration in the process of dynamic piling,has been widely used and accepted,but the calculation of coefficients in the formula is a complicated and difficult process.In fact,the dynamic piling process is to use the huge instantaneous force generated in the collision between the hammer core and the top of the pile to drive the pile.The change of force during collision is very sharp,accompanied by strong loss of mechanical energy,such as sound,light,heat and so on.Based on the collision principle of basic physics and the law of conservation of momentum,taking hammer and pile as a system,the relation between hammer displacement and velocity is established,and the estimation formula of hammering force is deduced.It provides a new method to estimate the ultimate bearing capacity of pile foundation for selecting hammer of dynamic pile driving.