【作者】 邢心魁；

【导师】 吴敏哲；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2005， 博士

【摘要】 反射波法是目前最常用的桩基完整性检测法,其理论基础为一维波动理论,资料分析方法主要靠时域内直观分辨,定性评价,很多情况下其精度和可靠性不能满足工程需要。为改进目前反射波法桩基动测技术存在的问题,本文对实际桩～土体系条件下波传播规律及测试信号分析技术两个方面进行了较系统研究。 1、对模型桩进行了反射波法动力测试,并对试验场地土进行了动力试验。获得试验场地土动力特性指标和桩周有土、无土两种情况下模型桩的反射波特性曲线,并进行了系统分析。 2、采用有限元瞬态动力计算,探讨了桩～土体系条件下桩中波传播速度与幅值衰减规律与桩周土性的关系。 3、将小波分析理论引进反射波法桩基动测领域,阐述其基本理论并研究了小波分析在测试信号除噪、土阻力波分离及浅部缺陷桩分析等方面的初步应用。 在上述工作基础上得到以下主要成果: (1)受桩身几何效应影响,桩中脉冲波传播速度不再为恒值,随着传播距离增加出现大于、等于和小于波在一维杆中的传播速度三个阶段; (2)桩周土模量增大使波速增高,阻尼系数增大使波速减小;实际波速取决于二者共同作用的结果,往往使波速降低。 (3)桩中波传播速度与桩周土状态有关,使得上、下行波速度不同,上行拉力波速小于下行波速,而上行压力波速大于下行波速。 (4)下行压缩波与上行波衰减规律不同,其中上行拉力波比下行波衰减快;上行压缩波比下行波衰减慢。下行波的衰减规律符合指数衰减,但上升波的衰减并不符合这一规律。目前工程实践中统一按指数规律放大的方法来减小土阻力作用具有一定的局限性。 (5)采用小波分析技术对信号除噪、浅部缺陷桩动测信号分析及土阻力波分离等几种典型情况的信号分析方法进行了研究,实现了复杂情况下的动测信号的简化分析; (6)桩～土体系条件下实测反射波动测曲线的小波分析结果表明,不同频段的波速变化不大,但其波幅吸收系数近似与频率呈正比。更多还原

【Abstract】 Pulse Echo dynamic pile testing method is the most often used pile integrity test methods. Base on the one-dimensional stress-wave theory, the test data can be interpreted by intuitive method in time-domain or frequency-domain. Because of the qualitative analysis the precision and the reliability usually can’t satisfy the engineering demand.In order to resolve the problem in pile integrity testing, the characteristic of wave propagating along the pile-soil system and the test signal interpret methods have been studied systematically.(1) Performed the model pile testing and the soil samples dynamic testing. Soil dynamic properties index about the test site were acquired, pulse echo dynamic test figures of model piles enclosed with soil and without soil were also acquired and analysed systematically.(2) By means of finite element method, the relationship of wave speed and wave amplitude decay to soil behaviour were researched.(3) The wavelets analysis method was introduced into the field of pile integrity testing, the wavelet theory was also introduced and some applications of the wavelet analysis to pile testing were attempted,such as denoise methods, the ways of separating soil resistanced wave from the test curve and the interpreting means of testing figure for shallow defected piles.Base on the above works, some positive results were acquired as follow:(1) Because of the size effect, the traveling speed of pulse wave along the pile is no longer a constant value. With the increasing of propagating distance, the wave speed may be larger, equal, or slower than the one-dimensional rod wave speed.(2) The static resistance from soil around pile can increase the wave travel speed, but the damping can decrease the wave speed, the final results depend on the superposition of both effects and usually it makes the wave speed slower.(3) traveling speed of wave along the pile is also affected by the state of stress, the wavespeed between upward and downward is different, wavespeed of upward tensile wave is swifter than the downward speed, the wavespeed of upward compression wave is slower than the downward wavespeed.(4) Wave amplitude decay in different ways by downward compressive wave and upward wave, the upward wave decay slower than the downward wave. Downward wave amplitude decay in negative exponential function, but the upward wave amplitude is not the case. In practice, engineers and technicians always magnify the test data according to the exponent rule to decreasing the effect of soil.(5) To make use of wavelet analysis, the test signal can be decomposed on wave band, so the complex signal become several simply signals, so we can treat it in an easy way.(6) Some analysis on test data for the pile enclosed by soil show that different wave bands travel in similar speed, but the amplitude decay severe with the frequency increasing.更多还原