Ambient Temperature Sensitivity in Seepage Velocity Identification: A Thermal Response Analysis Using Point Heat Source Method

Temperature compensation is a common treatment to eliminate the influence of temperature-dependent physical and mechanical properties of medium on measurement results. To investigate the effects of ambient temperature on seepage identification results using the point heat source (PHS) method, Considering the temperature nonlinearity of hydrothermal parameters, numerical simulation was conducted on the cooling pattern of a PHS in porous medium. Then, an experimental system for calibrating the relationship between seepage velocity and its discriminant index (ξ) was established. This system can create a uniform seepage field with controllable flow velocity in porous medium. The thermal response laws of the PHS in porous medium were investigated under different ambient temperatures and seepage velocities using the quasi-distributed seepage monitoring system with a mobile PHS. The results show that ambient temperature and seepage velocity have negligible effects on the heating phase of the PHS when heating voltage and duration remain constant, making temperature rise amplitude unsuitable as a discriminant index of seepage velocity. Both ambient temperature and seepage velocity influence the cooling phase of the PHS. The absolute value of ξ decreases with the increase of ambient temperature when the seepage velocity is constant. A multilayer neural network incorporating both ambient temperature and ξ as input parameters, with seepage velocity as output parameter, achieves satisfactory identification performance.