基于加热弱光纤阵列分布式测量技术的大坝渗流监测新方法

新型弱光纤阵列分布式测量技术是大坝渗流监测的新技术。根据弱光纤光栅测温原理、对流传热方程组和牛顿冷却公式,推导出热光纤渗流监测理论公式。设计了基于加热弱光纤监测渗流的圆筒模型试验,通过光纤周围温度场与渗流场的耦合关系,间接获得圆筒模型的渗流状态。试验结果表明,温度边界层是影响温度场和渗流场的重要因素,渗流水温度对温度边界层影响较大;渗流量与温差ΔT的线性度高;渗流流速u在0.02~0.08cm/s时与ΔT/θ(θ为光纤测量温度与渗流水温度之差)拟合关系式的各项系数与理论推导公式相近。

A New Method of Dam Seepage Monitoring Based on Heating Weak Fiber Array Distributed Measurement Technology

The new-type of weak fiber array distributed measurement technology is a new technology for dam seepage monitoring.According to the principle of weak fiber grating temperature measurement,convection heat transfer equation and Newton cooling formula,the theoretical formula of thermal fiber seepage monitoring was derived.A cylinder model test was designed based on heating weak fiber to monitor the seepage flow.The seepage state of the cylinder model was obtained indirectly through the coupling relationship between the temperature field and the seepage field around the fiber.The test results show that the temperature boundary layer is an important factor that affects the temperature field and seepage field.The temperature of the seepage water has a great impact on the temperature boundary layer;The linearity of the seepage flow and the temperature difference(ΔT)is high;The seepage flow velocity is 0.02-0.08 cm/s,the coefficients of the fitting relationship between the seepage velocity u andΔT/θ (θis the difference between the temperature measured by the optical fiber and the seepage water temperature)are close to the theoretical derivation.