变阻抗桩非自由端竖向瞬态激振动力响应分析方法及应用

Dynamic response analysis method for variable impedance pile under vertical transient non-free end excitation and its application

针对变阻抗桩非自由端竖向瞬态激振时反射波曲线复杂的问题,基于一维黏弹性杆件纵向振动理论和土体平面应变模型,建立简化的桩-土竖向振动数学模型。采用升余弦函数模拟瞬态激振力,通过矩阵运算和积分变换求解得到桩身任意位置动力响应的半解析解,并结合海上带长钢护筒灌注桩的低应变实测数据进行对比分析。结果表明,该方法能够反映混凝土顶面以上钢护筒端部反射信号特征,进一步结合设计、施工参数对类似工况进行模拟,有助于分析变阻抗桩非自由端激振形成的复杂反射波曲线及识别桩身缺陷。

In view of the problem that the reflected wave curve is complicated when a variable impedance pile is under vertical transient non-free end excitation,we build a simplified mathematical pile-soil vertical vibration model on the basis of the longitudinal vibration theory of one-dimensional viscoelastic rods and the soil plane strain model.We adopt the raised-cosine function to simulate the transient excitation force,obtain a semi-analytical solution to the dynamic response at an arbitrary position on the pile stem through matrix operation and integral transform,and compare with the measured low-strain data about offshore bored piles with long steel casings.The results show that the proposed method demonstrates the characteristics of the reflected signal at the end of the steel casing above the concrete top.Furthermore,combining the above method with the simulation of similar working conditions under design and construction parameters is conducive to analyzing complicated reflected wave curves produced by non-free end excitation applied to variable impedance piles and identifying the pile stem defects.