邹锦阳, 张雅婷, 丁欣, 姚建铨. 激光致声混凝土内部空洞检测[J]. 红外与激光工程, 2023, 52(1): 20220306. DOI: 10.3788/IRLA20220306
引用本文: 邹锦阳, 张雅婷, 丁欣, 姚建铨. 激光致声混凝土内部空洞检测[J]. 红外与激光工程, 2023, 52(1): 20220306. DOI: 10.3788/IRLA20220306
Zou Jinyang, Zhang Yating, Ding Xin, Yao Jianquan. Detection of internal cavities in concrete with laser-acoustic method[J]. Infrared and Laser Engineering, 2023, 52(1): 20220306. DOI: 10.3788/IRLA20220306
Citation: Zou Jinyang, Zhang Yating, Ding Xin, Yao Jianquan. Detection of internal cavities in concrete with laser-acoustic method[J]. Infrared and Laser Engineering, 2023, 52(1): 20220306. DOI: 10.3788/IRLA20220306

激光致声混凝土内部空洞检测

Detection of internal cavities in concrete with laser-acoustic method

  • 摘要: 激光致声混凝土内部空洞检测技术是一种针对混凝土脱空鼓包现象的遥感检测技术,具有检测快速,非接触等特点,满足了在一些不方便进行接触式检测的场景下对混凝土内部空洞进行识别的需求。该技术的实现主要分为声波的激发以及声波的探测。文中聚焦声波激发这一部分,用加速度传感器替代激光测振仪,搭建了一套激光致声混凝土内部空洞检测系统,并对内部预制空洞的混凝土试块进行了检测。实验发现混凝土内部空洞的存在会改变空洞上方结构的抗弯刚度,当存在外部激励时,空洞上方的结构将会出现弯曲振动的现象,该振动的频率接近于振动结构的一阶固有频率。使用高功率密度的脉冲激光器可以方便地激发出缺陷区域的弯曲振动,当空洞缺陷较浅时,可以根据弯曲振动在频域的特征响应判断内部是否存在空洞。随着空洞深度的增加,空洞上方结构的抗弯刚度逐渐增强,弯曲振动的振幅减小,仅凭特征频率将难以实现内部空洞的识别。在这种情况下,可以利用表面振动信号的加速度能量谱来表征振动能量,通过振动能量的高低判断混凝土内部是否存在空洞。基于上述理论,成功探测到了混凝土内部深度为150 mm的空洞,验证了利用激光致声技术检测混凝土内部空洞的可行性。

     

    Abstract: The technology of detection of internal cavities in concrete with laser-acoustic method is one kind of remote sensing detection technology for internal cavity of concrete, which has the characteristics of fast detection and non-contact, meeting the needs of identifying the internal cavity of concrete in some cases where it was not convenient to conduct contact detection. In this paper, focusing on the part of acoustic excitation, a laser acoustic concrete internal cavity detection system was built using accelerometers instead of laser vibrometers, and concrete specimens with internal prefabricated cavities were inspected. It was found that the presence of internal concrete voids would change the flexural rigidity of the structure above the voids, and when there was external excitation, the structure above the voids would show the phenomenon of bending vibration, the frequency of which was close to the first-order intrinsic frequency of the vibrating structure. The bending vibration in the defect area can be easily excited by using a high-power density pulsed laser, and when the cavity defect was shallow, the presence or absence of cavity inside can be judged by the characteristic response of the bending vibration in the frequency domain. As the depth of the cavity increased, the flexural rigidity of the structure above the cavity gradually increased, the amplitude of the bending vibration decreased, and the identification of the internal cavity will be difficult to be achieved by the characteristic frequency alone. In this case, the acceleration energy spectrum of the surface vibration signal can be used to characterize the vibration energy and determine whether there were cavities inside the concrete by the level of vibration energy. Based on the above theory, the cavity with a depth of 150 mm inside the concrete was successfully detected, which verified the feasibility of using laser acoustic technology to detect the cavity inside the concrete.

     

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