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One of the major concerns in the behavior of a dam are the changes to exit gradient and the impact on the slope stability under sudden drawdown conditions. Drawdown increases the gradient difference between the internal areas (i.e. dam body) and the external areas (i.e. the reservoir). It can also cause increased seepage forces on the upstream slope and on the foundation surface which may result in movement of soil particles in the flow direction causing erosion problems. In this paper, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to determine the upstream exit gradients and slope stability. GeoStudio programs using the FEM are used to conduct both steady-state and transient analyses. Three typical designs of earth dams, with and without the core, are used to study the seepage and the upstream slope stability before and after the upstream drawdown event. Water flux, flow direction, exit gradient, and the slope factor of safety are calculated in each case. The results show that the core is important in reducing the flux through the dam. Constructing a cutoff under the core increases the efficiency of the core and lowers the phreatic line. However, the results also showed that the submerged weight increases when the earth dam is constructed with a core or with a complete low permeability cutoff. Increasing the submerged weight, in turn, causes higher water flux to flow out of the dam under the drawdown condition increasing the exit gradient. The exit gradient at the upstream slope may reach critical levels and cause failure of the dam. The factor of safety of the slope is also reduced because of increasing the buoyancy of the soil at the upstream side of the dam. Some preliminary results are presented in this paper.

One of the major concerns in the behavior of an earth dam is the change in the exit gradient and the impact on the slope stability under drawdown conditions. Drawdown can cause increased seepage forces on the upstream slope which may result in the movement of soil particles in the flow direction and cause erosion problems. In this research, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to study exit gradients and slope stability under both steady-state and transient conditions. The results show that a central core is important in reducing the flux through the dam. Constructing a cutoff under the core further increases the efficiency of the core and lowers the phreatic line. However, it is seen that the submerged weight increases when the earth dam with a core or with a complete cutoff which causes higher water flux to flow out of the dam under the drawdown condition. The exit gradient at the upstream slope may reach critical levels and cause failure of the dam due to erosion. Adding an upstream filter is studied as a possible solution to this problem. Two configurations of the filters are modeled and the slope filter configuration performed best in reducing the exit gradient at the upstream face. A low permeability core with a cutoff increases deformation of the soil because of increased saturated areas in the upstream region. The factor of safety of the slope is also reduced because of the increased buoyancy of the soil at the upstream side of the dam. The soil properties of the upstream filter have a significant influence on the slope stability against sliding. An upstream slope filter increases the stability of the slope while a central filter decreases it.

Seepage analysis of earth dams is one of the major interesting points in geotechnical engineering. The amount of water seeping through and under an earth dam together with the distribution of the water pressure can be estimated by using the theory of flow through porous media which is one of the most valuable analytical tools available to the engineer. In this paper, the finite element method is utilized to solve the governing equations of flow through earth dams. The computer program Geo-Slope is used in the analysis through its sub-program named SEEP/W. Eight node isoparametric elements are used to model the dam and its foundation, while mapped infinite elements are used to model the problem boundaries. A case study is considered to be Al-Adhaim dam which consists of zoned embankment 3.1 km long. The dam at its actual design is analyzed using the program SEEP/W. Then several analyses are carried out to study the control of seepage in the dam through studying the effect of several parameters including the permeability of the shell material and the presence of impervious core and its location and thickness. It was concluded that the presence of clay core has an important effect on decreasing the exit gradient, which may increase in the order of 300% when the core does not exist and the factor of safety may be critical when the water level in the reservoir is at 143.5 m. The sloping core of Al-Adhaim dam is the best design for core than other choices since it permits the lowest values of seepage and provides the lowest exit gradients.

Abstract Recycling plastic waste has always been vital for sustainability, besides exploiting that waste to improve the mechanical properties of concrete mixtures which contribute effectively in the field of civil engineering applications. In this research, the enhancement of compressive, tensile and flexural strength of concrete mixtures was explored using both adding plastic fibers and HP-570 super-plasticizer. Plastic waste, as fibers, was mixed with an Ordinary Portland cement for a total volume of concrete of 0.5, 1, 1.5 and 2%, then the HP-570 super-plasticizer was added and the procedure was re-done. At the age of 28 days of curing, the compression strength was increased by (13.2%) while both tensile and flexural strengths were increased significantly by (117.4%) and (207.5%) respectively when using the plastic as fiber with 2%. Further improvement was gained by adding the HP-570 super-plasticizer for the concrete mixture.

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