Analysis of the seepage impermeability line of roller-compacted concrete dams founded on weak rock formations

Seepage control in dam foundations is of critical importance for both safety and operational considerations. In particular, the design of impermeable structures becomes more complex under heterogeneous foundation conditions created by weak sedimentary rocks, such as those of the flysch sequence. Therefore, in dam engineering, it is essential to perform reliable seepage analyses and evaluate the performance of seepage control systems in accordance with the foundation conditions. This thesis aims to analyze the cutoff wall lengths to be constructed using the slurry trench method in roller-compacted concrete dams founded on weak sedimentary flysch formations through finite element analyses. In this context, seepage analyses were conducted using the CAD-based finite element programs SEEP/W and SLIDE. Different lithological ratios, layer thicknesses, and material permeabilities were considered to evaluate alternative cutoff wall lengths, and the results obtained from both programs were compared, showing close agreement. Sections with a 10% silt content exhibited higher permeability and total seepage, whereas sections with 50% to 70% silt content demonstrated that the cutoff walls were largely adequate from both technical and economic perspectives. Keywords: Flysch formation, seepage analysis, rolled compacted concrete dam, slurry trench, plastic concrete.