Question

In a syphon aqueduct, the most severe condition of uplift on the floor occurs when

• A. the canal and drainage runs full
• B. the canal runs full; the drainage channel is dry, and the water table is at the stream bed
• C. the canal is dry, the drainage floor is at HFL, and the water table is at the HFL of the drainage flow
• D. the canal runs full; and the drainage is dry

Answer 1

The correct option is C the canal is dry, the drainage floor is at HFL, and the water table is at the HFL of the drainage flow



A syphon aqueduct is constructed where the water surface level of the drain at high flood is higher than the canal bed. The designer must consider the upward thrust that might act during high floods in the natural stream when the stream water flows under pressure below the trough of the canal and for worst condition, the canal may be assumed to be dry at that time.