Seepage monitoring is an important issue in the health monitoring and performance evaluation of geotechnical engineering, and one of the effective ways to monitor seepage is the thermal method. Based on the coupling effects between the seepage field and the temperature field, a point heat source (PHS) method is presented in this paper. The PHS seepage monitoring system was composed of a monitoring tube, multiple sensing–heating elements, a regulated power supply and a demodulator. The sensing element, a fibre Bragg grating (FBG) sensor, is integrated with the heating element (a ceramic heating tube). To optimise the monitoring scheme of this system, the influence of sensitivity-related factors on the identification effects of seepage is studied. The implementation pattern of the sensing–heating element, dimensions of the monitoring tube, heating voltage and heating period were used as factors for calibration experiments at different seepage velocities. The results reveal the following: (a) both implementation patterns, with heat conduction glue or a copper tube filled in the gap between the FBG sensor and the ceramic heating tube, obtained good monitoring results; (b) the dimensions of the monitoring tube significantly influenced the effects of seepage identification, where the larger the gap was between the monitoring tube and the sensing–heating element, the worse were the results of monitoring; (c) within the relevant ranges, the heating voltage and period had nearly no effect on the monitoring results. Based on these conclusions, a monitoring scheme that combines the sensing–heating element with heat conduction glue filled in the gap and monitoring tube of 20 mm dia. was chosen for a leakage monitoring experiment. Three patterns of the leakage passage were tested in the experiment, and each was tested with three values of leakage intensity. The results show that leakage was accurately determined by the PHS seepage monitoring system, and its estimates of flow flux agreed well with empirical values.

中文翻译：

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使用点热源的敏感性分析和渗漏监测

渗流监测是岩土工程健康监测和性能评价中的一个重要问题，热法是监测渗流的有效方法之一。基于渗流场与温度场的耦合效应，本文提出了一种点热源（PHS）方法。PHS渗流监测系统由监测管、多个传感加热元件、稳压电源和解调器组成。传感元件是光纤布拉格光栅 (FBG) 传感器，它与加热元件（陶瓷加热管）集成在一起。为优化该系统的监测方案，研究了灵敏度相关因素对渗流识别效果的影响。传感加热元件的实现方式，监测管的尺寸，加热电压和加热时间被用作不同渗流速度下校准实验的因素。结果表明：（a ) 两种实施方式，在FBG传感器与陶瓷加热管之间的间隙中填充导热胶或铜管，均获得了良好的监测效果；( b ) 监测管的尺寸对渗流识别的效果有显着影响，监测管与传感加热元件之间的间隙越大，监测结果越差；( c)在相关范围内，加热电压和加热周期对监测结果几乎没有影响。基于这些结论，一种将传感-加热元件与填充在间隙中的导热胶和直径为 20 mm 的监测管相结合的监测方案。被选择用于泄漏监测实验。实验中测试了三种泄漏通道模式，每种模式都测试了三个泄漏强度值。结果表明，小灵通渗流监测系统准确地确定了泄漏量，其对流量的估计与经验值吻合良好。