【作者】 燕艳朋；

【导师】 王运生；

【作者基本信息】 郑州大学 ， 道路与铁道工程， 2011， 硕士

【摘要】 随着各类工程的不断建设,锚杆应用范围的不断扩展,导致锚杆用量急剧增长,也使得锚杆质量对工程安全性的影响越来越受重视,因此提高锚杆检测精度的呼声也越来越高。作为国家自然科学基金资助项目(50874035)“基于伪随机信号的锚杆动态响应与智能检测研究”的一个子项,本文从完善锚杆检测体系出发,提出以可控震源技术实现对应力波检测信号的精确控制,并调制出具有良好自相关特性的Chirp信号作为震源信号。笔者利用编制的Delphi应用程序,借助对扫频方式和频谱范围的变换,实现了包括正弦信号、雷克子波信号和三类Chirp信号等多种检测信号。通过一系列室内试验对信号自相关特性和衰减特性等特点进行的对比研究,验证了Chirp信号频带宽、能量大、自相关性良好、易于检测等特点,非常适合作为锚杆检测震源信号。借助计算机声卡和超磁共振等技术,将Chirp信号和可控震源引入到锚杆质量检测领域,也成为本论文的创新所在。基于以上先进理念,笔者实现了一套试验装置,并利用它进行了一系列室内模拟试验,从而对各类信号的自相关特性以及衰减特性有了更深入的认识,主要的研究成果如下：(1)正弦波信号自相关特性非常差,不适合作为激振信号。雷克子波信号虽然自相关特性较好,但由于是短脉冲信号,信号传播过程中衰减过快,也不适合作为锚杆检测所用震源信号。(2)三类Chirp信号均具有良好的自相关特性,即使当其反射信号叠加在一起时,其相关信号仍然十分清晰,具有良好的抗噪性能。三类Chirp信号均存在一个最佳频谱区间,并大致存在于2k-20kHz至4k-20kHz这一区段内,但准确的区间位置有待进一步深入研究。(3)在室内模拟试验条件下,正弦波信号自相关特性表现仍然很差,而雷克子波信号在接收信号振幅较小情况下,自相关性效果也非常差。在相同试验条件下,试验Chirp信号即使在振幅很小的极端条件下,仍能保持良好的自相关性效果,初至时间非常明显。(4)通过对衰减系数的计算比较,发现试验Chirp信号传播过程中能量衰减均较小,并且自相关特性变差的速度要明显慢于振幅的衰减速度。同等试验条件下,试验Chirp信号的能量衰减特性基本接近,相对来说,2k-20k线性Chirp信号或4k-20k指数Chirp信号的表现更加优异。对震源信号形式的定量控制技术,特别是对信号频率的控制,是目前该方向研究的处女地,本课题的研究完善了锚杆质量检测研究体系,也为应力波检测方法的发展贡献了微薄的力量。试验装置在室内试验的应用效果较好,基本实现了预期目标,但由于该技术涉及范围广泛,相关内容仍需进一步完善。更多还原

【Abstract】 With the continuous construction of various projects, the application of rockbolt is expending, which leads to sharp increase in use of rockbolt, and also makes more and more attention to the relationship between quality of rockbolt and safety of projects. And the voice of demanding for improving detection accuracy becomes stronger and stronger.For perfecting the detecting system of bolt-anchoring quality, we put forward vibroseis technique to accurately realize the control of stress wave signal, and Chirp signal, which has good autocorrelation, is adopted as vibroseis signal. With application compiled by Delphi, many kinds of signals are modulated by changing sweep mode and frequency range, like sinusoidal signal, ricker wavelet signal and three types of Chirp signals, et al. Through a series of laboratory tests on signals’ autocorrelation and attenuation, we verify that Chirp signal has wider frequency band, higher energy, better autocorrelation, and is easier to be detected, which is quite suitable to be detecting signal for vibroseis.With computer sound card, supraconduction magnetic resonance, and other technologies, Chirp signal and vibroseis are introduced to the field on testing of bolt-anchoring quality, which is also my innovation in this thesis. Based on the advanced idea, we realize a test device, and carry out a series of laboratory experiments with it. Therefore, we comprehend more about autocorrelation and attenuation of the signals, and the main results are as follows:(1) The autocorrelation of sinusoidal signal is so poor that it’s unsuitable as detecting signal for vibroseis. Although ricker wavelet signal has better autocorrelation, because it’s short pulse signal, and the attenuation of signal is too fast, which makes it excluded also.(2) Three kinds of Chirp signals all have good autocorrelation, even when the reflected signals add together, which reveals its antinoise performance is satisfying. The Chirp signals all have a optimal frequency range that generally exists in the section between 2k-20kHz and 4k-20kHz, but further research is needed for its exact location.(3) In our testing condition, the autocorrelation of sinusoidal signal remains badness. When the amplitude of received signal is smaller, the autocorrelation of ricker wavelet signal becomes extremely poor. In the same condition, Chirp signal could maintain good autocorrelation, and the first arrival time is very obvious, even on the extreme conditions when the amplitude of received signal attenuates observably.(4) Through the comparison of attenuation coefficient, we find, for testing Chirp signals, the energy of received signals attenuates more slowly, and the rate of autocorrelation’s deterioration is evidently smaller than the rate of amplitude’s decay. In the same condition, their character is close to each other in energy attenuation. Relatively, the linear Chirp signal of 2k-20k and the exponential Chirp signal of 4k-20k have more excellent performance than others.The quantitative control of vibroseis signal, especially for the control of signal’s frequency, is still the virgin land in this field. The research on this subject perfects the testing system of bolt-anchoring Quality, and definitely makes some contribution to the development of stress wave detection method. The performance of our test device in laboratory tests is satisfying comparatively, and we generally achieve the anticipated result. As the technology involves plentiful knowledge of many fields, there still needs further improvement.更多还原