The injection curtain is assumed to be an effective method for 
reducing infiltration characteristics, such as flow rate, pore 
pressure, and outlet gradient across the earthen dam foundation.
To investigate the influence and performance of injection curtain, 
the Izdihar dam is selected as a case study for modeling using the 
numerical analysis software SEEP/W. The objective of this study 
is to investigate the injection curtain in terms of different 
numbers and horizontal spacing between injection curtains. The 
results revealed that by increasing the horizontal distance 
between the double curtains from the axis under the central core, 
the flow rate and the exit gradient are decreased while increasing 
the horizontal distance, the flow rate is decreased by about 20% 
and the exit gradient is decreased by about 46%. Similarly, by 
increasing the distance between double curtains to X/L core =1, the 
pore pressure is decreased below the dam. Increasing the number 
of curtains to three is important for minimizing the outlet 
gradient and flow rate to optimize the safety of the earth dam, the 
exit gradient decreases up to 21% and flow rate up to 17%, 
respectively