- 2075 Bhadra · 2 marks
Confined and unconfined flow
Short answer
Confined flow has fixed boundaries allowing direct flow net construction, such as under concrete dams. Unconfined flow has a free surface (phreatic line) at atmospheric pressure whose position must be determined by trial, as in seepage through earth dams.
What is confined and unconfined flow in seepage flow?
Confined flow: seepage in which all the boundaries of the flow region are fixed and known, so the flow lines and the flow net can be drawn directly. Examples: flow beneath a concrete dam or weir, flow under a sheet pile wall, flow through a pervious foundation.
Unconfined flow: seepage in which one boundary of the flow region, the upper flow line (phreatic line or line of seepage), is not fixed and must be found by trial, because it is a free surface at atmospheric pressure. Example: seepage through the body of an earth dam, or flow to a well in an unconfined aquifer.
| Point | Confined | Unconfined |
|---|---|---|
| Upper boundary | Fixed (impervious boundary) | Free surface (phreatic line) |
| Pressure on top flow line | Greater than atmospheric | Atmospheric |
| Example | Under a concrete dam | Through an earth dam |
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Confined and unconfined aquifers · Soil Mechanics, chapter 6
- Earth dam flow type · Soil Mechanics, chapter 7
- Seepage in inclined permeable layer · Soil Mechanics, chapter 6
- Sheet pile seepage quantity numerical · Soil Mechanics, chapter 7
- Impervious dam seepage discharge · Soil Mechanics, chapter 7
- Confined versus unconfined aquifer · Engineering Geology II, chapter 3 · asked 4×
- Confined versus unconfined aquifer · Engineering Geology I, chapter 6 · asked 2×
- Control of sub-surface water and seepage · Transportation Engineering I, chapter 4 · asked 15×
- Seepage and phreatic line: horizontal filter at toe · Hydropower Engineering, chapter 4 · asked 3×