- 2075 Bhadra · 2 marks
Why a filter on dam downstream
Short answer
A downstream filter prevents piping by allowing seepage water to exit while retaining soil particles. It keeps the phreatic line within the dam, preventing slope saturation and slumping, reduces pore water pressure for improved stability, and safely collects and drains seepage to avoid toe softening.
Why is a filter used on the downstream of an earth dam?
A filter (drain) is provided on the downstream side of an earth dam because
- it lets the seepage water leave the dam body freely while holding back soil particles, so piping is prevented;
- it keeps the phreatic line (top flow line) inside the dam and away from the downstream face, so the slope does not become saturated and slump or erode;
- it reduces pore water pressure in the downstream shell, which increases the stability against slope failure;
- it collects the seepage and drains it safely, avoiding softening and sloughing of the downstream toe.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Earth dam with filter, seepage quantity · Soil Mechanics, chapter 7
- Earth dam flow net and discharge · Soil Mechanics, chapter 7
- Earth dam flow type · Soil Mechanics, chapter 7
- Top flow line, dam with horizontal filter · Soil Mechanics, chapter 7
- Impervious dam seepage discharge · Soil Mechanics, chapter 7
- Earth dam with drain pipe: phreatic coordinates · Hydropower Engineering, chapter 4
- Reservoir intake for an earth dam · Water Supply Engineering, chapter 5 · asked 2×
- Filter material in earthen dam · Hydropower Engineering, chapter 4
- Seepage discharge through dam body (k = 1×10⁻⁶ m/s) · Hydropower Engineering, chapter 4