Performance evaluation method for measuring crack width of tunnel lining detection instruments

Ensuring the accuracy of tunnel lining inspection instruments is crucial for maintaining tunnel safety. Given the complexity and variability of lining crack morphologies and widths, it is particularly important to conduct more in-depth verification of the measurement performance of existing tunnel lining crack detection instruments. To this end, our study carefully crafted standardized simulated crack boards using rigid plastic and restored crack morphologies by designing specific skeleton lines. These crack boards not only lay a solid foundation for theoretically calculating crack widths but also provide an innovative method for evaluating the performance of lining crack detection equipment. To create differentiated crack widths and establish their standard values, we designed seven straight lines with varying slopes on the edges of the plastic boards to form the skeleton lines of the cracks and precisely adjusted the spacing between them. Furthermore, this study introduces a new method of stratified data analysis, comparing calibrated and measured values and their relative errors through statistical analysis to verify the measurement stability of the equipment. The research results show that the equipment can effectively identify various crack widths. However, when measuring narrower cracks (<0.20 mm), the relative error of the equipment is relatively high (reaching 48.50%). Nevertheless, when measuring cracks with widths between 0.4 and 0.6 mm, the relative error is significantly reduced to 11.55%. For cracks wider than 0.60 mm, the error is stably controlled below 5%. These findings underscore the central role of standardized crack boards in tunnel lining inspection, enhancing the accuracy and reliability of the inspection process and facilitating consistent inspection results. Through this standardized crack simulation approach, we can provide more reliable data support for the maintenance and evaluation of tunnel linings, ultimately improving overall tunnel safety.