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All-season monitoring of concrete repair in an urban tunnel in Brussels using embedded ultrasonic transducers with emphasis on robustness to environmental variations
Journal of Civil Structural Health Monitoring ( IF 4.4 ) Pub Date : 2021-05-15 , DOI: 10.1007/s13349-021-00486-9
Cédric Dumoulin , Arnaud Deraemaeker

This paper presents the results of a long-term concrete monitoring campaign in an underground tunnel in Brussels. The system consists of several pairs of embedded ultrasonic piezoelectric transducers arranged in a pitch-catch configuration which have been placed in the concrete ceiling of the tunnel in areas where old concrete was demolished and then repaired. The monitoring system is fully automated and sends the recorded signals to a cloud-based system in our university where they are post-processed to extract indicators of structural changes in the monitored regions, and send automated email reports. A first period of six months is studied, during which the monitored areas have been repaired with skim mortar. The post-processing of the measured signals allows to identify clearly the time of repair in each zone and the evolution of the hardening process of the repair mortar. A second monitoring period of one year is then studied where it is found that despite the proposed improvement to the time stretching technique used to filter out the effects of changing environmental conditions, our indicators are still showing variations in periods when the temperature is very high in the tunnel. A method based on observed statistical correlations between the indicators computed in the different regions is then proposed and shown to be very efficient to remove the remaining variability and make the system very robust to environmental changes. Extreme value statistics is also presented as a tool to establish relevant thresholds for alarm-triggering with a very low level of potential false alarms. With all these developments, the monitoring system can automatically detect structural changes in the tunnel in real time while being robust to unavoidable changes in the environmental conditions in the tunnel.



中文翻译:

使用嵌入式超声换能器对布鲁塞尔城市隧道中的混凝土维修进行全季节监控,重点是应对环境变化的鲁棒性

本文介绍了布鲁塞尔地下隧道中长期混凝土监测活动的结果。该系统由几对嵌入的超声波压电换能器组成,这些换能器以节距捕获的方式排列,这些换能器已被放置在隧道的混凝土顶棚中,这些区域是旧混凝土被拆除然后修复的区域。监控系统是完全自动化的,并将记录的信号发送到我们大学的基于云的系统中,在该系统中对其进行后处理,以提取受监控区域中结构变化的指标,并发送自动电子邮件报告。在六个月的第一阶段进行了研究,在此期间,用脱脂砂浆修复了受监控的区域。对测量信号的后处理可以清楚地确定每个区域的修复时间以及修复砂浆硬化过程的演变。然后研究了第二个监视期,即一年,发现尽管建议改进用于滤除环境条件变化影响的时间延长技术,但我们的指标仍显示出温度非常高的时期的变化。隧道。然后提出了一种基于观察到的在不同区域中计算出的指标之间的统计相关性的方法,该方法显示出非常有效的方法来消除剩余的可变性并使系统对环境变化非常鲁棒。还提供了极值统计信息,作为建立相关阈值以触发警报的阈值,其潜在错误警报的级别非常低。通过所有这些开发,监视系统可以实时自动检测隧道中的结构变化,同时对隧道环境条件不可避免的变化具有鲁棒性。

更新日期:2021-05-17
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