To prevent scouring at the termination point of a structure, providing a ________________ at the exit is necessary?
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Answer: A. Vertical cutoff
Explanation
A vertical cutoff increases the sub-surface seepage length, reducing exit hydraulic gradients safely. Placing this barrier at the structure end prevents high-velocity water from eroding foundation soil. It intercepts concentrated seepage paths and protects the downstream riverbed from localized undermining. Water seeping beneath hydraulic structures exerts upward pressure and creates erosive exit velocities. Bligh and Lane creep theories emphasize adding vertical cutoffs to lengthen the seepage path. Scour occurs when high shear stresses detach and transport bed particles away from foundations.
Weirs and barrages incorporate deep downstream cutoffs to ensure long-term stability against piping failure. Preventing foundation erosion avoids catastrophic structural settlements and costly rehabilitation projects. Civil engineers routinely include sheet piles or concrete cutoffs in hydraulic design specifications. Option B provides surface energy dissipation but does not lengthen sub-surface creep paths. Option C refers to a river training structure used for flow diversion rather than exit protection. Option D offers surface armor against wave action rather than stopping subsurface piping failure.
- Subject
- Agriculture
- Category
- Agriculture
- Topic
- —
- Difficulty
- medium
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