Numerical simulation of active heat injection near an earth-concrete dam interface for the identification of anomalous seepage
University of New Brunswick
Active heat injection and temperature monitoring are methods that may be useful for the detection of anomalous seepage in embankment dams. The main objectives of this research were to investigate, using numerical simulation, the feasibility of using active heat injection and distributed temperature monitoring to identify anomalous seepage at the interface between earth embankments and concrete structures, and to quantify seepage rates for a hypothetical zone of enhanced permeability at the clay core-concrete interface. A three-dimensional finite element model was developed to simulate the injection of heat into a vertical borehole drilled within concrete with an orientation parallel to the clay core-concrete interface. Anomalous seepage at the interface was created by increasing the permeability in a 3 m thick zone and imposing a range of hydraulic gradients. For a borehole-interface separation distance of 1.5 m, the maximum temperature deviations within the heat injection borehole, due to the anomalous seepage, are less than 0.6°C. For borehole-interface separation distances of 1.0 m and 0.5 m, the simulations reveal deviations in the range of l.0-5.1°C during the heat injection phase, and less than l .2°C during the cooling phase. The temperature deviations are simulated to be less than l.0°C at a temperature monitoring borehole located 1.0 m down gradient of the heat injection location for the borehole-interface separation distances of 1.5 m and 1.0 m. These findings suggest that the heat injection and monitoring boreholes would need to be located less than 1.0 m from the interface to ensure maximum temperature deviations of l .0°C or greater. Provided the heat injection location is within 1.0 m of the interface, it is concluded that interpretation of temperature data collected prior, during, and following heat injection should enable the identification of anomalous seepage zones.