基桩低应变检测中波速测不准问题的研究  

STUDY OF INACCURACY OF P-WAVE VELOCITY IN PILES BY LOW STRAIN INTEGRITY TESTING

作　　者：胡新发[1] 柳建新[1] 

机构地区：[1]中南大学地球科学与信息物理工程学院,湖南长沙410083

出　　处：《岩石力学与工程学报》2013年第S2期4183-4189,共7页Chinese Journal of Rock Mechanics and Engineering

摘　　要：通过低应变法检测基桩的现场试验,对比研究传感器安装位置对首波幅值及初至时间、桩底反射幅值及到达时间、检测波速等的影响特征。试验表明,由于首波时间滞后的影响,对于相同长度的桩,桩径越大,检测波速偏高越多;对于相同桩径的桩,长度越短,检测波速偏高越多。为提高低应变法检测的准确性,经理论分析,建立考虑时间滞后的针对灌注桩和预应力管桩的完整桩纵波速度计算公式、桩身缺陷位置计算公式,并首次提出灌注桩桩身下部缺陷段的平均波速计算公式。实践证明,提出的计算公式能正确反映桩身的实际纵波速度、桩身缺陷实际位置,较现有的计算公式有明显的优越性。Field testing of piles using low strain method is carried out to study the effects of sensor position and excitation point on the first amplitudes,first-break times,reflection amplitudes and times of the end of the piles and testing wave velocities. The test results show that for the same length of piles,the larger the pile diameter is, the more occurrences of testing wave velocity is on the high side,while for the same diameter of piles,the shorter the pile length is,the more occurrences of testing wave velocity is on the high side. In order to improve the testing accuracy of wave velocity,using theoretical analysis,formulae considering the time lag are established for computing P-wave velocity in an integrate pile and the position of shaft defects of cast-in-place piles and prestressed pipe piles. For the first time formula is established to calculate the average velocity of the lower part of defect segment of the cast-in-place pile. Practice prove that the proposed formulae can correctly reflect the actual P-wave velocity of pile and actual position of defects in a pile,hence the formulae have obvious superiority over the existing ones.

关 键 词：桩基础 基桩检测 低应变法 纵波 波速 

分 类 号：TU473.1[建筑科学—结构工程]