钢筋混凝土桩在粘性土中打桩时的混沌效应分析

Analysis of Chaos of Pile Driving for Reinforced Concrete Piles in Cohesive Soil

研究在粘土中打桩出现的混沌现象.首先利用史密斯提出的打桩波动方程作庞加莱截面图,得到打桩中混沌现象的基本特征.接着分析庞加莱截面图,找到贯入度和速度比值最大的点,即为功耗最小的点.同时,通过曲线拟合证明了功耗最小时的锤重和落高满足重锤轻击的施工经验.根据此原理改变冲击力和初值的大小即可得到打桩时不同截面尺寸方形桩和圆形桩功耗最小时所需的锤重和落高.研究结果表明不同截面尺寸的方形桩和圆形桩与其桩顶冲击力,落高和锤重满足一定的关系曲线,因此施工中根据它们的函数关系选取相应的锤重和落高可以节省功耗,降低造价.

The chaos phenomenon in pile driving in cohesive soil is presented.Firstly,the pile wave equation that Smith put forward is used for painting Poincare section,and then basic features of chaos are obtained.By analyzing Poincare section,apoint with which the ratio of penetration to velocity is the largest is discovered,and that is to say,energy consumption is the lowest at this point.Moreover,the relationship between hammer weight and dropping height is proved to satisfy the construction experience of light blow with heavy hammer through curve fitting.So according to the theory,the value of impact force and initial value can be changed to get the hammer weight and dropping height for different square and circular piles under the lowest energy consumption.The results show the relationships between the square or circular pile with different cross-section and its impact force on pile top,hammer weight and dropping height satisfy a certain function equation,respectively.Hence,the corresponding hammer weight and dropping height can be selected to save energy consumption and reduce the cost during construction according to their functional relation.