Your question has two parts
1) How to control seepage?
2) Stability of dam with cheaper material
Concerning your question 1, seepage's briefly could be categorized as the one seeping through the structure above the ground and second, we called it under seepage. The under seepage are prevented through the construction of vertical barriers and foundation cutoffs are constructed primarily from one of three materials 1) Compacted impervious earth in excavated trenches 2) Steel sheet piling and 3) Concrete walls. Other method include use of cement grout through fissured rocks under dams and slurry trench foundation cutoff.
You might have heard about 1450MW Ghazi Barotha hydel power project located in Attock, Pakistan. The seepage upstream and downstream of the barrage controlled through the laying of filtered materials covered with heavy concrete blocks. Through the center of dam, beneath the ground level, vertical wall had been constructed in bentonite slurry and this method has been used to reduce the quantity of under seepage by lengthening the seepage path. Horizontal drainage system installed at downstream to safely drain the seeped water. Additionally relief well have been installed to control the seeping water under the foundation of the earth dam.
Concerning your second question, stability is one the most important design parameter of the dam. The economics of the dam apart from other factors also depend on the availability of the nearby material to be used in the dam construction. Large quantity of material available close to the dam would cost less than the material to be transported from far quarry. There are various method for calculating the stability of the dam for example 1) sliding surface method 2) stress method.
The dam stability could not be comprised with cheaper material. A non-stable dam means 1) embankment and foundation piping 2) Differential Settlement 3) Embankment and foundation slides 4) Earthquake damages 5) Damages due to borrowing animals 6) Damages due to liquefaction and other natural destructive forces. The material to be used in dams shall be able to resist the disturbing forces mentioned above and shall remain stabilized during the service life.
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Masood Ahmad R.Eng, M.ASCE
Assistant Executive Engineer
Pakistan Public Works Department
Islamabad
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Original Message:
Sent: 04-14-2018 11:03
From: Shahid Ali
Subject: Design of Small Earth fill Embankment Dam
Hello...
I have my final year project (undergraduate) in design assessment of an Earth fill dam. In which I will be doing modifications in the design of an existing Dam (Latambar Dam, Karak, Pakistan). If you have any idea about how to control seepage and increase the stability of Dam with cheaper material or any slope variations it would help me. Thanks...
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Shahid Ali S.M.ASCE
Mardan
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