Crack detection is an important issue in the health monitoring and performance evaluation of concrete structures. Based on the heat transfer theory, a temperature tracer method and a monitoring system for crack detection in underwater concrete structures are presented in this paper. The system is composed of an integrated sensing and heating system, a monitoring tube, and multiple casing tubes. The inner diameter of the casing tube should be larger than the outer diameter of the monitoring tube so that there is a certain gap between the casing tube and the monitoring tube to form a cavity. Water fills the cavity along the crack face when the underwater concrete structure cracks, resulting in a change in the surrounding medium at the cracked site. Thus, the cooling rate of the heat source in the monitoring tube corresponding to the cracked site will be accelerated. Crack identification can be done based on a comparative analysis of the cooling curves of the heat source in the uncracked and cracked states. The effects of cavity geometry size and intensity of heat source on crack identification are studied using numerical simulations and crack detection tests. Both simulations and test results confirm the feasibility of the proposed crack detection method.

中文翻译：

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用于水下混凝土结构裂缝检测的温度示踪法

裂缝检测是混凝土结构健康监测和性能评估中的重要问题。基于传热理论，提出了一种温度示踪法和水下混凝土结构裂缝检测监测系统。该系统由一个集成的传感和加热系统，一个监控管和多个套管组成。套管的内径应大于监测管的外径，以使套管与监测管之间有一定的间隙以形成空腔。当水下混凝土结构开裂时，水沿开裂面充满空腔，导致开裂部位周围介质发生变化。从而，监测管中与破裂部位相对应的热源的冷却速度将加快。可以基于对未破裂和破裂状态下热源的冷却曲线的比较分析来确定裂纹。利用数值模拟和裂纹检测试验研究了腔几何尺寸和热源强度对裂纹识别的影响。仿真和测试结果均证实了所提出的裂纹检测方法的可行性。