Investigation of seepage near the interface between an embankment dam and concrete structure: monitoring and modelling of seasonal temperature trends
University of New Brunswick
The temperature monitoring method, which makes use of the fact that increased seepage flow may locally alter the natural temperature distributions within embankment dams and their foundations, is regarded as a useful approach for seepage monitoring and evaluation. In this study, spatial and temporal variations of temperature have been monitored and modelled at the interface between the compacted clay till core of an embankment dam and an adjoining concrete diversion sluiceway structure at the Mactaquac Generating Station, located on the Saint John River near Fredericton, NB. The measurements were acquired using a fibre optic distributed temperature sensing (DTS) system installed in a 50 m long borehole drilled into the concrete structure within 0.5 m of the interface. Two significant temperature anomalies were observed. A three-dimensional finite element model was developed to simulate the temperature distributions within the dam resulting from the seasonal variations of air and headpond water temperatures. Anomalous seepage zones near the interface were simulated in the concrete and along the dam/concrete interface (in the embankment) independently, and in both locations simultaneously. The results demonstrate that passive DTS monitoring is a feasible approach to identify potential seepage zones near an embankment dam/concrete structure interface. Anomalous temperature zones, and associated gradients, can be clearly identified and numerical modelling can indicate, in some cases, whether such anomalies are related to seepage in the concrete or in the embankment; however, other details such as the water flow path geometries and seepage rates are not as well constrained.