The scientific and practical value of this research appears in recognizing the characteristics of the clay soil, which is located in Alnabeck, and used in constructing ALwagar earth fill dam. We will study five samples chosen from the materials site Hofar ALmlagea and which will be used in constructing ALwagar earth fill dam through which some Geo-geometrical characteristics like (Liquid Limit, Plasticity Limit, plasticity index, Consistency Index, Liquidity Index, Clay activity, collapse degree) will be determined. Depending on the Results of this study, we used international classifications (Casagrande classification – Unified Soil Classification System) to study the soil of the studied area. We made use of the results of the experimental study to determine the position of soil according to the international classification, and we suggested some solutions to improve the characteristics of the soil which is used in constructing soil dams.