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大直径管桩在低应变检测中应力波的传播是一个三维波动问题。将桩周土、桩芯土和桩底土对桩的作用简化为文克尔弹簧,将激振力用半正弦脉冲模拟,建立了大直径管桩在瞬态集中荷载作用下的振动响应计算模型,采用分离变量法和常数变易法求得了波动方程的时域解表达式。将该时域解与采用数值傅立叶逆变换计算得到的时域响应进行了对比验证,进一步将时域解析解计算结果与试验值进行了对比,验证了其合理性。采用得到的时域解计算分析了桩顶速度时域响应特性,结果表明:入射波到达时间和结束时间与波的传播距离成正比,从0°点到180°点基本呈线性变化;激振点的入射波结束时间等于输入脉冲宽度,其余测点的入射波结束时间与入射波到达时间的差值与输入脉冲宽度相等;入射波峰值对应的时间在激振点最小,从0°点到135°点逐渐增大,在135°点到180°点之间基本保持不变。
The propagation of stress waves in large-diameter pipe piles during low-strain testing is a three-dimensional fluctuation problem. The effect of pile surrounding soil, pile core soil and pile bottom soil on the pile is simplified as a Wenker spring. The excitation force is simulated by half-sine pulse, and the calculation model of the vibration response of large diameter pipe pile subjected to transient concentrated load is established , The time-domain solution of the wave equation is obtained by using the method of separating variables and constant variation method. The time-domain solution is compared with the time-domain response calculated by numerical inverse Fourier transform. The calculated results of time-domain analytical solution are compared with the experimental values to verify the rationality. The time-domain solution was used to analyze the time-domain response characteristics of pile top velocity. The results show that the incident arrival time and the end time are proportional to the propagation distance of the wave, and linearly change from 0 ° to 180 °. Point of the incident wave is equal to the end of the input pulse width, the remaining points of the incident wave arrival time and arrival time difference between the input pulse width equal to; incident peak corresponding to the minimum time in the excitation point from 0 ° to 135 ° points gradually increased, in the 135 ° point to 180 ° points between the basic remain unchanged.