大直径桩扭转波法测试的数值分析

Numerical analysis of torsional wave test for large-diameter piles

文章采用交错网格有限差分法对大直径桩扭转波法测试进行数值分析,将桩-土系统视为三维线弹性体,建立了轴对称条件下大直径桩瞬态扭转振动模型;根据初边值条件,利用交错网格有限差分法对波动方程进行离散求解,得到了瞬态扭矩作用下的桩顶速度响应,讨论了三维干扰及缺陷响应特点。结果表明:越靠近桩顶中心,桩底反射波与入射波振幅越大;大直径桩桩顶扭转波测试结果面临三维干扰波影响,激振脉冲越窄,三维干扰越强烈;缩径处产生的反射波与入射波同向,而扩径处产生的反射波与入射波反向。扭转波法可为传统纵波法测桩提供有效补充或参照。

The staggered grid finite difference method is used to numerically analyze the torsional wave test of large-diameter piles.The pile-soil system is regarded as a three-dimensional linear elastic body,and the transient torsional vibration model of large-diameter piles under axisymmetric conditions is established.According to the initial-boundary conditions,the wave equation is solved discretely by using the staggered grid finite difference method.The velocity response of pile top under transient torque is obtained,and the characteristics of three-dimensional interference and defect response are discussed.The results show that the closer the center of pile top is,the greater the amplitude of reflected wave and incident wave is.The torsional wave test results of large-diameter pile top are affected by three-dimensional interference waves.The narrower the excitation pulse is,the stronger the three-dimensional interference is.The reflected wave generated at the necking is in the same direction as the incident wave,and the reflected wave generated at the bulb is opposite to the incident wave.The torsional wave method can provide an effective supplement or reference for the traditional longitudinal wave method.