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Abstract
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This paper aims to thoroughly investigate the effect of weakness in the upstream impervious blanket of
earthfill dam on the seepage behavior. For this end, a limited zone with high permeability is considered in
various situations of impervious blanket. Then, for each situation, the discharge value and seepage pattern
through the foundation is determined by performing 2D finite element seepage analysis via GeoStudio
software.
Regarding to the analysis result, the location defected zone in upstream impervious blanket directly
influences the seepage pattern through dam body and foundation. If the defected zone is occurred in the
situations close to the dam core, escaping water from weakness zone of impervious blanket impact the clay
core water tightening performance and water potential head drop is not completely occurred in clay core.
From the erosion potential view, the critical condition is directly depended on the foundation permeability.
For most permeable foundation, the gradient of 5.6 is recorded for the defected zone located out of dam
body in defected zone. For this type of dam, the gradient in foundation is insignificant. If the foundation
has lower permeability and defected zone is occurred in impervious blanket next to clay core connection
point, the foundation beneath the defected zone is susceptible to erosion.
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