基于流-热耦合模型的土石坝渗流热监测研究

为有效应用基于分布式光纤测温的渗流热监测技术，需研究待监测区的背景温度场特征。为此，建立了土石坝饱和-非饱和瞬态渗流场与温度场耦合模型（流-热耦合），模型考虑了热对流、热传导和热扩散效应，温度边界按周期性气温考虑，且相关参数按非线性考虑，如流体黏度的热效应、导热系数受含水率影响等，其仿真结果更接近土石坝温度场的真实状态。基于典型算例，讨论了与大气温度相关的周期性波动温度场特征。计算结果表明：温度场受坝体渗流和气温的影响，库水及气温是两个重要热源，饱和带的温度受库水渗流控制，非饱和带主要受气温控制，具有季节波动特征；在土石坝心墙部位若发生集中渗漏，渗漏通道附近岩土体的温度受库水影响；若在心墙上敷设分布式光纤传感器，很容易捕捉到渗漏点位置及渗漏发生的时刻。渗流热监测技术在理论上可以反映渗流场的时空分布特征，在资料分析中还应关注由气温波动引起的温度异常。

Numerical simulation of embankment dam seepage monitoring with temperature based on thermal-hydro coupling model

In order to implement the seepage monitoring with temperature in embankment dam with the popular distributed fiber optic temperature sensor system (DTS), it’s necessary to study the background characteristics of temperature field. Herein, a saturated-unsaturated seepage field and temperature field coupling model (thermal-hydro coupling, i.e. T-H) is established. The model considers the heat convection-conduction-diffusion, as well as the boundary periodically fluctuation with atmosphere temperature. Some parameters are considered nonlinearly so that the result of simulation is closer to the true state of dam temperature field. For instance, the fluid viscosity is influenced by temperature and thermal conductivity is influenced by moisture, and so on. A clay core embankment dam is taken as a case study. It is shown that the temperature field within the dam has the characteristics of seasonal fluctuation, which is controlled by seepage and atmospheric temperature. Specifically, the heat from the reservoir controls the temperature variation of the saturated zone and the heat from atmosphere controls that of the unsaturated zone. If the core wall leaks, the temperature nearby will reduce as cold reservoir water flowing into. In this case, the distributed fiber sensors lying on the core wall can be used to detect spatial and temporal distributions of leakage. The conclusions are drawn as follows that the seepage monitoring with temperature is effective in theory. In the data analysis, particular attention should be paid to the temperature anomalies caused by atmosphere temperature.