Study on active heating method of seepage micro-velocity monitoring

Seepage is an important issue of engineering safety, and its monitoring methods are diverse, among which temperature tracing methods are widely applied. In this study, a temperature rise–seepage velocity formula which takes account into natural convection with heat source is obtained. The temperature and the corresponding seepage velocity of calm water and 10 ⁻⁶ cm·s ^− 1 to 10 ⁻³ cm·s ^− 1 are obtained by experiments. Results reveal: 1. After heating for approximately 100 s, the temperature becomes relatively stable, and using this stable temperature for monitoring yields better results. 2. As the temperature difference between the initial water temperature and the room temperature (Td) increases, the temperature rise (Tr) increases, and the relationship is obtained. 3. The device's bias towards the downstream boundary leads to an abnormal temperature rise pattern. Thus the device is placed in the central part, and the water is heated 180 s. The temperature rises are processed, and a temperature rise-flow velocity formula for seepage monitoring by boreholes with active heating is derived. This formula considers the natural convection and extends the seepage velocity range to the micro-seepage velocity range. It holds significant importance for seepage monitoring using the temperature tracing method with active heating, especially for the monitoring of micro velocity.