Horizontal view of a numerically calculated temperature field in the vicinity of a heat source after 12 h of heating. The vertical line source is located at the origin of the coordinate system and has a source strength of 150 W/m. The surrounding soil has a porosity of 10% and a heat conductivity of 1.2 W/m/K. On the left hand side water with an initial temperature of 17.3 °C enters the model area with a filter velocity of 10-5 m/s. It is clearly visible that a significant part of the induced heat is carried off by the percolating flow.
IN SITU MEASUREMENT OF SEEPAGE FLOW VELOCITY (HPM)
The most critical hydrodynamic parameter for material transportation phenomena by seeping water is the local pore velocity. Regions with high pore velocity are most likely prone to internal erosion. Up to now, critical pore velocities for the onset of internal erosion have been determined theoretically by using particle size distributions and measured hydraulic gradients. The applicability of theoretically calculated pore velocities is rather limited and in most cases questionable. In order to address this problem GTC® developed a temperature based method - the Heat Pulse Method (HPM). With the HPM it is possible to determine pore velocities in the range from 10-7 m/s up to 10-3 m/s. Thus, allowing the in situ determination of this important hydro dynamical parameter for the first time.

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     - Heat-Pulse-Method (TSM4.pdf, 134kb)