The line in a dam section in within a dam section below which there are positive hydrostatic pressure within the dam?

Explanation:

• The line that separates the saturated zone (where water pressure is positive) from the unsaturated zone in an earthen dam is known by all three names.
• Below this line, the soil is fully saturated, and positive hydrostatic (pore water) pressure exists.

Additional InformationSeepage Line:

• Represents the upper boundary of the flow zone through the dam body.

• Water seeps below this line and exerts positive pressure.

• Often identified through flow nets or finite element modeling in seepage analysis.

Phreatic Line:

• Another name for the seepage line, specifically in earth dams.

• Lies within the downstream face and is often parabolic in shape.

• Above this line, soil is unsaturated, and below it, fully saturated.​

Saturation Line:

• Term used interchangeably to indicate the limit of saturation within the soil mass.

• Denotes the start of hydrostatic pressure from capillary tension to positive pore pressure.