低应变动测法在桩基质量检测中的应用

Application of Low Strain Dynamic Test Methodto Pile Foundation Quality Inspection

桩基低应变法虽简单快捷,但检测过程中影响因素较多,导致桩检人员对桩质量分类不准确。为提高桩检人员技术水平,本文论述了低应变动测法的基本要求和声波传播特性及其在实践中的应用。研究结果表明,均匀等截面杆件的声波传播特性不变;缩颈桩截面阻抗由大变小,入射波与透射波同向,波速增大;扩颈桩截面阻抗由小变大,入射波与透射波反向,波速减小;无缺陷桩截面阻抗和波速不变;桩端进入软弱下卧层时,桩底无反射或者反射不明显。掌握声波在不同桩体的传播特性,能避免桩检人员因经验导致的误判。

Although low strain method is simple and rapid for integrity test of pile foundation engineering,there are many influencing factors in the detection process,which often lead to inaccurate pile quality classification.In order to improve the technical level of inspection personnel,the basic requirements of low strain dynamic test method,the characteristics of acoustic wave propagation and its application in practice are discussed in the paper.The results show that acoustic wave propagation characteristics of rods with uniform cross-section remain unchanged.The impedance of necked pile decreases from large to small,the incident wave and the transmitted wave are in the same direction,and the wave velocity increases.The section impedance of the belled pile increases from small to large,the incident wave and the transmitted wave are reversed,and the wave velocity decreases.The section impedance and wave velocity of the pile without defect remain unchanged.When the pile tip enters weak substratum,there is no reflection at the pile bottom or the reflection is not obvious.Mastering the propagation characteristics of acoustic wave in different piles can avoid misjudgment caused by experience for pile inspectors.