Steady-state seepage through and below earthen dam under seismic condition: insights into hydrological mechanism

Most of the studies in the literature focus on analyzing water flow within earthen dam under static condition. The objective of this study is to analyze water flow mechanisms within earthen dam under seismic condition. To achieve this purpose, a series of numerical simulations were conducted to model earthen embankment based on a real case scenario based on dam built in eastern province of India (i.e., South 24 Parganas in West Bengal). Further the effect of sheet pile as a seepage cutoff has been evaluated with variations in sheet pile length and location under steady-state settings for both static and seismic conditions. The study was carried out using FLAC2D version 5.0 and SEEP/W version 12.0 for a dam. The results show that pore pressure is high on the upstream side of the sheet pile during continuous seepage and quickly decreases along the sheet pile itself for all sheet pile positions. In seismic instances under steady-state conditions, when pore water pressure increases, the factor of safety decreases by 45% to 50% as compared to similar static cases. This is due to an increase in seepage force. As the sheet pile is cut off, the overall factor of safety increases as compared to the condition with no sheet pile. This study is though simplified; however, it provides insights into water flow pattern within earthen dam that need to be considered for preliminary design in regions, which are subjected to seismic loads.