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In this study, the use of combined drain has been suggested as an alternative for triangular toe drain in a homogeneous earth dam. The main idea used in this research is to reduce the volume of drain materials that are manufactured and simultaneously achieving better hydraulic performance. To study this idea, at first, the hydraulic performance of the combined drain and the influence of replacing the triangular toe drain with this type of drain is investigated using the small-scale physical modelling. Then large-scale numerical simulation was performed by developing a numerical model. The designed triangular toe drain height was reduced by 20, 30, 40 and 50%, and part of the remaining material was placed horizontally alongside the reduced triangular toe drain. The results showed that using combined drain with similar hydraulic performance to triangular toe drain models, saved 18 to 60% on the volume of drain materials for the models provided. Finally, the appropriate dimensions of combined drain are proposed based on the saving of material used. At the end, by applying dimensional analysis method, the dimensionless charts are presented to estimate the seepage quantity through the section of the homogeneous earth dam with combined drain. [ABSTRACT FROM AUTHOR]

The main goal of this study is to investigate the effect of soil properties such as permeability on the dispersion and movement of a water dissolved contaminant in three types of soil in saturated and 2D conditions. The experimental modeling was conducted using a constructed sand box. In order to evaluate the effect of soils particle size on the distribution and self‐remediation of the contaminant, three types of soil, as coarse, medium, and fine‐grained sand were used. Results of experiments showed that, at the first 25% of the test time, the contaminated area reduction rate in all three specimens varies significantly, so that for the medium and coarse sand, it is 2.2 and 3 times that of fine sand, respectively. The contaminant width reduction at the first 25% of the test time was 5%, 6%, and 35% for the fine, medium, and coarse sand, respectively, while the contaminant length reduction was 13%, 18%, and 37% for the fine, medium, and coarse sand, respectively. In addition, by comparing the contaminant movement in the saturated and semi‐saturated areas, it was observed that the longitudinal and transverse movement of the contaminant under the water level are almost 2.5 times of the semi‐saturated area. Practitioner points: Reduction rate of solution area in fine, medium and coarse‐grained sample are nearly convex, linear and concave‐shaped, respectively.The remediation process in saturated zones is implemented in both directions with higher intensity in a shorter time than unsaturated zones.In the strip formed plumes, the volume of the self‐remediation is proportional to the time intervals during the test.In the elliptic masses the self‐purification amount is lower at the beginning, due to the small cross‐section ending of the contamination mass. [ABSTRACT FROM AUTHOR]