Abstract
Seepage and water flow into soil are of the critical factors in the design of earth dams. There are various methods to control seepage in the dam foundation. One solution is the use of plastic concrete cutoff wall. Due to a higher hydraulic gradient in the union area and pressure increase of embankment above the wall by time, a considerable consolidation occurs in the wall. Therefore, crack in the wall, water seepage and erosion in the union area may occur. Hence, one of the items considered in earth the dams sealing system of design especially for plastic concrete cutoff walls is union area. This paper focuses on the effects of penetration depth of cutoff walls into the core of earth dams. To this aim, Anbaran dam located in the north-west of Iran was selected as a case study. Various penetration depths of cutoff walls including 0, 1, 2 and 3 m were considered. A two-dimensional model was defined and the results were compared together. For the numerical modeling and analysis of stresses and displacements in the mode of statics, including the construction stage and the first impoundment stage, GeoStudio-2007 and FLAC2D softwares were used, and for the dynamic stage FLAC2D was used. The results show that the penetration depth of wall plays an effective role in the flow rate of water, hydraulic gradient, stress and displacement of wall and union area. The results of numerical model revealed that, as the penetration depth increases, stresses and displacements of union area increase while the hydraulic gradient and seepage at the union area decrease. Finally, by analyzing the dam behaviorial parameters such as stress, displacement, seepage and hydraulic gradient, and also considering the economic and implementation aspects, the penetration depth of 2 m is chosen as an optimum penetration depth of this case. In this state, the maximum magnitudes of vertical and horizontal stresses are 2371 kPa and 728 kPa, respectively and the maximum magnitudes of vertical and horizontal displacements are 19.36 cm and 7.42 cm, respectively. The amount of seepage under the dam body is 3.330 × 10−6 m3/s/m and the maximum hydraulic gradient in the wall is 39.222. However, to find an optimum penetration depth of cutoff wall into the clay core, numerical analysis with corresponding specifications are strictly needed, indeed.
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