SPRING 2023, Vol 9, No 2, JOURNAL OF HYDRAULIC STRUCTURES Shahid Chamran University of Ahvaz Journal of Hydraulic Structures J. Hydraul. Struct., 2023; 9(2):101-117 DOI: 10.22055/jhs.2023.44272.1258 Numerical study concerning the different drainage systems in earth dams Mahmoud M. Mostafa 1,2 Shen Zhenzhong 1 Abstract One of the most popular tools for dealing with the seepage problem in embankment dams is using different types and shapes of downstream drains. So, the paper presents a comprehensive study of the different drainage systems through such dams. Many earth dam models are investigated through the SEEP/W model representing different dimensions and geometry of downstream drains. A comparison is carried out between the present study and previous experimental and numerical studies and the results of the present study are almost close to the previous studies. The present work concludes that the most influential factor in a horizontal drain is the length, and the thickness has a negligible effect. The reasonable length ratio of a horizontal drain (L/B) is about 0.34 according to the minimum seepage. The angle of toe drains has a slight effect on the different seepage parameters. The performance of the inclined chimney drain is better than the vertical drain to control the seepage. Keywords: Earth dams, Seepage control, Drainage systems, SEEP/W. Received: 12 July 2023; Accepted: 16 August 2023 1. Introduction Earth embankment dams are widely built in water streams and rivers and are generally economical compared with other dams. Embankment dams represent about 70% of dams in the world [1]. Seepage is one of the most serious stability concerns of embankment dams. The most popular reasons for embankment dam collapse are overtopping and seepage [2]. It was found that about 35% of dams' failures all over the world were due to seepage [3]. The main two problems of seepage through embankment dams are; the amount of seeped water which is of great importance for storage dams, in addition to the stability of the earth dam against seepage [4]. Many precautions have been studied for controlling seepage and avoiding or preventing such failure. Using different drainage systems and cores, grout curtain have been the main methods studied for seepage control through or beneath earth dams. 1 College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China. 2 Civil Engineering Department, Assiut University, Assiut 71516, Egypt. E-Mail: eng.mmm91@aun.edu.eg (Corresponding author)