4.1. SEEPAGE THROUGH SOIL
SEEPAGE THROUGH SOIL:
· Is a process in which liquid leaks through a porous medium from high head towards low head.
· Although flow velocity of water during seepage is very small (as this flow is Laminar) but in reality, it poses many problems such as:
o Losses of water reservoir
o Reduction in effective weight of soil
o Uplift pressure below dam
o Piping failure, which can lead to sudden structural collapse
Because of these risks, it is important to calculate and control seepage flow.
FLOW NETS:
· Seepage flow is calculated with the help of flow nets and is based on Laplace’s equation of continuity. 3D flow is complex; thus, we cover 2D dimensional seepage flow.
A flow net consists of two sets of curves:
Flow lines → represent the path followed by water particles
Equipotential lines → represent equal head (hydraulic potential)From a completed flow net, the quantity of seepage can be calculated
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| FLOW NET |
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| length of smallest flow element near downstream side |
The smallest flow element near the downstream side is especially important, as it is used to estimate the exit gradient, which helps check the risk of piping or heave.
💡 Seepage may seem slow and harmless, but as engineers we know its impact can be critical. What seepage control method do you think is most reliable in practice—cut-off walls, drainage blankets, or something else? Share your thoughts in the comments!
Seepage control really depends on soil conditions and engineering project types, but id had to pick up one reliable method, I would go with cut-off walls. They are effective because they directly reduce seepage pressure by cutting through permeable layers and forcing water to take much longer path. This is significantly lowers the risk of piping beneath dams and levees. That said, drainage blankets are very practical when compete cut-offs are not feasible, since they safely collect and release seepage without building up pore pressure.
ReplyDeleteCut-off walls are the most reliable way to control seepage in major structures like dams because they block deep water flow and handle strong pressure. They’re expensive and tricky to build, but worth it when safety is critical. Drainage blankets are cheaper and easier to install, and they work well for shallow seepage and slope stability, though they’re less effective in loose or sandy soils. Other methods like grouting, relief wells, and upstream blankets can help in specific cases, but overall, cut-off walls are the strongest and most consistent option when seepage could cause serious damage
ReplyDeleteCut-off walls are one of the most effective techniques for seepage control in large projects like dams because they stop deep water flow and resist high pressure. While their construction is costly and technically demanding, they are essential where maximum safety is required. Drainage blankets, in contrast, are less expensive and easier to build. They are suitable for managing shallow seepage and improving slope stability, though they perform poorly in loose or sandy soils. Other measures such as grouting, relief wells, or upstream blankets may be applied in particular situations, but overall, cut-off walls provide the most secure and consistent protection against serious seepage problems.
ReplyDelete