COMPARATIVE STUDY OF SEEPAGE THROUGH AN EARTH DAM

Abstract

Earth dams are commonly used in many nations because of their ease of building and maintenance. This study aims to determine the seepage discharge in an earth dam by building twenty-four models in a hydraulic flume and altering various input parameters. A dam with a central impermeable core and a homogeneous earth dam has been built in a hydraulic flume in the lab. The earth dam also has a filter to prevent the phreatic line from cutting the downstream slope of the dam, which might cause damage. Some of the characteristics studied in this study include upstream slope, downstream slope, longitudinal slope, upstream slope, downstream slope, changing the top and bottom widths of the dam while keeping the upstream and downstream slopes the same, changing the height and length of the earth dam, central core width, filter length, and filter height; and their impact on seepage and the phreatic line. A fluorescent dye was used to identify a phreatic line in the experimental model, then compared to the phreatic line developed from Seep/w in Geostudio software. The numerical analysis results were found to be consistent with the experimental findings. Dupuit's equation, Casagrande's, Schaffernak's, and Pavlovsky's solutions were used to validate homogenous physical experimental and numerical models. The stability of the upstream and downstream slopes of the earth dam was also examined using Slope/w in Geostudio software, which was confirmed to be safe under full reservoir conditions. The temperature measurement was used to investigate the seepage fluctuation in the earth dam. In a hydraulic flume, seventeen models of earth dams were built by altering geometrical and flow input parameters. Temperature measurement along the phreatic line was done using a digital thermometer and compared to the phreatic line produced by Seep/w. The phreatic line derived from the experimental models was identified using a fluorescent dye. Temp/w was used to model temperature variation inside an earth dam due to the convective flow of water. Temperature variation in an earth dam by the experimental model was compared with the contours of temperature obtained using temp/w and were in good agreement. It was discovered that as the longitudinal slope, downstream slope, and dam height are increased, the water flow accelerates, which leads to a rise in temperature variation of the earth dam due to increased convection and vice versa for the upstream slope. With the introduction of an impervious central core in the earth dam, the dam’s temperature reduced significantly due to the reduced flow vi rate of water. The inclusion of a downstream filter stopped the phreatic line from cutting the earth dam's downstream face. The temperature was increased drastically due to an increased water flow rate due to the filter's increased length and thickness. Temperature measurement proved to be a cost-effective method of detecting seepage in an earth dam. The water flux in an earth dam was simulated in a hydraulic flume by altering geometrical and flow input parameters to determine heat and water flux. A Homogeneous, as well as earth dam with a clay core, was built-in a hydraulic flume. Heat flux was calculated in the experimental model using temperature observations. Seep/w was used to calculate water flux, and temp/w was used to calculate heat flux in a finite element model of the earth dam. When comparing homogeneous models to central impermeable core models, a considerable decrease in heat and water flux was observed. When the length and longitudinal slope of the downstream filter was increased, the heat and water flow increased, and vice versa when the upstream slope and clay core thickness were increased. Heat flux measurements proved to be a cost effective option for measuring water flux and seepage in an earth dam.