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Numerical methods
for seepage
through earthen
dams analysis
Roland YONABA, Research Assistant
Presented at Cape Coast University
August, July the 19th, 2013
PRESENTATION OUTLINE
• Dams ?
• Earthen-made dams (& facts)
• Overview of the seepage phenomenon
• The research problem
• Perspectives for further research
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DAMS ?
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EARTHEN MADE DAMS
Dams made with heavily compactedearthen materials (sand, clay, silt,…)
Convenient to retain a low water height(<= 10 m)
Cheap ()
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EARTHEN DAMS FACTS (IN B.F.)
• Since 1920. Common uses
– irrigation
– water supply
– cattle watering
• Almost 2000 dams in Burkina Faso nowadays
• Quite all of them are earthen-made
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THE SEEPAGE PROBLEM
• Wet areas downstream ARE NOT naturalsprings. Usually.
• Water always follows the path of leastresistance.
–Carry material throughout the dam
–Erosion → Collapse
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EVALUATING SEEPAGE (ACTUAL METHODS)
• The hydraulic method : 𝑞 = 𝑘𝐻𝑖
• Kozeny’s parabola
𝑦0 = 𝑑2 + ℎ2 − 𝑑 𝑡ℎ𝑒𝑛 𝑞 = 𝑘𝑦0
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HOW CAN WE ACCURATELY EVALUATE SEEPAGE ?
• Numerical models solve propagative motions
• Types of numerical methods
• Finite Volumes (3D space)
• Finite Elements and Finite Differences (2Dspace)
• Why Finite Differences ?
– Fast setup for modelling
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HOW CAN WE ACCURATELY EVALUATE SEEPAGE ? (Cont’d)
• General objective
– Build a general purpose model that can predictheadline, pressure, flow distribution and evaluateseepage quantities through an earthen dam.
• Assumptions
– Soil is uncompressible and isotropic
– Flow is steady and laminar : Darcy’s Lawapplies
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ENGINEERING EXAMPLE
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ENGINEERING EXAMPLE (Cont’d)
PERSPECTIVES FOR FURTHER RESEARCH
• Benchmark (efficiency, accuracy)against FE, FV methods
• Investigate anisotropic damstructure models
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