ABSTRACT

A rapid and reliable method to detect the activation of contraction joint cracks is needed to assess the effectiveness of sawcut depth and timing on new concrete pavements and for forensic investigation. A one-sided ultrasonic measurement technique is presented that detects the existence of a contraction joint crack, which is not visible from the concrete slab surface. A multi-sensor ultrasonic array device is used to generate and receive ultrasonic shear waves (S-wave) across the inspected joint. The acquired time-domain signals are used to calculate a newly defined feature, called normalised transmission energy (NTE), across the joint. A laboratory experiment investigated the proposed technique on three 500 × 500 × 150 mm³ concrete specimens with 38 mm notch depth, the first without a propagated crack, the second with a narrow width crack, and the third specimen with a full-depth open crack. The laboratory results demonstrate that the NTE technique can identify the existence or not of a crack beneath the notch. Finally, the NTE technique coupled with a 2D decision boundary equation was field validated on 152 concrete pavement contraction joints with various slab thickness (e.g. 102 to 152 mm) and notch depths (less than 38 mm) from multiple projects in Illinois and Iowa (USA).

摘要

需要一种快速可靠的方法来检测收缩缝裂缝的激活，以评估锯切深度和时间对新混凝土路面的有效性以及法医调查。提出了一种单面超声波测量技术，用于检测混凝土板表面看不到的收缩缝裂缝的存在。多传感器超声波阵列设备用于生成和接收穿过检查关节的超声波剪切波（S 波）。获取的时域信号用于计算关节上新定义的特征，称为归一化传输能量 (NTE)。一个实验室实验在三个 500 × 500 × 150 mm ^{3上研究了所提出的技术}切口深度为 38 mm 的混凝土试件，第一个没有扩展裂缝，第二个有窄宽度裂缝，第三个有全深度开放裂缝。实验室结果表明，NTE 技术可以识别缺口下方是否存在裂纹。最后，NTE 技术与二维决策边界方程相结合，在伊利诺伊州和爱荷华州（美国）的多个项目的 152 个不同板厚（例如 102 至 152 毫米）和缺口深度（小于 38 毫米）的混凝土路面收缩缝上进行了现场验证）。