A concrete gravity dam is 100 ft long from upstream to downstream end. It is constructed on a stratum of sand–silt soil 40 ft thick. The coefficient of permeability for this soil is 0.1 ft per day....

A concrete gravity dam is 100 ft long from upstream to downstream end. It is constructed on a stratum of sand–silt soil 40 ft thick. The coefficient of permeability for this soil is 0.1 ft per day. Rock underlies the soil stratum. The bottom of the dam is 6 ft below the soil surface.

(a) For the condition where the height of water against the upstream face of the dam is 45 ft above the soil surface and the water level at the downstream end is just at the soil surface, draw the flow net for seepage beneath the dam and calculate the quantity of seepage in gallons per day per foot of width of dam.

(b) For the condition where the height of water against the upstream face of the dam is 35 ft above the soil surface and the water level at the downstream end is 5 ft above the soil surface, draw the flow net for seepage beneath the dam and compute the seepage in gallons per day per foot of width of dam.