Abstract
Design of earth dams and their issues during and after construction is very important for residents downstream of the dam because of the potential risks and possible breakdowns. In the design of dams, various forces influence the dam body, including uplift pressure and piping phenomenon which should be considered in order to ensure the safety of the dam. Among the measures taken to prevent the washing away phenomenon, the reduction of the output gradient, and the leakage discharge from beneath the hydraulic structures, construction of the grout curtain and installation of the drainage are applicable. Therefore, in order to investigate the effect of various parameters such as the gradient angle of the grout curtain, length, and distance and the number of grout curtains, as well as the length of the drainage on the pressure and output gradient of the numerical models, were considered in current study. For this purpose, the SEEP/W software was used for modeling on Sattarkhan Dam as a case study. The results of the analysis showed that the use of the Qa’im grout curtain at the upstream of the dam has the highest resistance against the pressure and piping phenomenon. The results also showed that increase in the length of the curtain of the water seal increases safety against uplift and piping phenomenon. The use of further spacing between the two grout curtains under the core of the dam led to increase in overall pressure or reduction in safety against uplift pressure. Increase in the length of the horizontal drainage reduced the effects of uplift pressure and output gradient. Results show that period of 70 to 110 degree is appropriate for curtain angle and setting curtain in upstream of dam core with angle of 70 to 80 degree is optimum and economic. A length of 30 m is optimum for curtain. The number of 2 curtains is also optimum. Studying various scenarios of distance of 2 curtains in dam core indicates that distance of 6 m is optimum and also length of 18 m for horizontal drainage is optimum.
Highlights
Following the construction of the dam, a large hydraulic slope is created upstream of the dam with regard to the downstream, which tends to leak and move the water from the upstream to the downstream
In order to study the effect of parameters in leakage, the SEEP/W model has been used and various models such as artificial neural network can be used for optimum design of the dam
The effects of various parameters of cutoff wall, including slope, length, distance, number of cutoff walls, effect of horizontal drainage and length of drainage on uplift pressure, and maximum exit gradient is studied, and these parameters are optimized in Sattarkhan Dam as a case study
Summary
Following the construction of the dam, a large hydraulic slope is created upstream of the dam with regard to the downstream, which tends to leak and move the water from the upstream to the downstream. The biggest problem is an increase in the outlet gradient of water, which causes float of the soil particles at the heel of the dam and as a result beginning of the movement of them. To control leakage from the dam, methods are used to reduce water leakage. One of these methods is the drilling of a trench after the dam and filling it with plastic concrete aggregates, as well as considering the horizontal drainage
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