Cross Drainage Works MCQ with answer and solution

Concept

Uplift Pressure in Siphon Aqueduct

Formula

N/A

Step-by-step solution

1. Analyze the condition for maximum uplift pressure on the floor of a siphon aqueduct. 2. Recognize that maximum uplift occurs when the drainage channel is at high flood level while the canal is completely dry. 3. Select Option A as the correct choice.

Explanation

Maximum uplift pressure on the floor of a siphon aqueduct occurs when the drainage channel is flowing at high flood level and the canal is completely dry. In this condition, the water in the drainage pushes upward with maximum hydrostatic pressure against the floor from below, while there is no downward weight of water in the canal above to counteract or balance this upward force.

Shortcut

To remember maximum uplift pressure on a siphon aqueduct floor, use the rule "High Drain, Dry Canal": - High Drain (Max Up): High flood in the drainage creates maximum upward hydrostatic pressure from below. - Dry Canal (No Down): An empty canal provides zero downward water weight to balance or counteract the uplift.

Common mistake

A common mistake is selecting Option C by assuming that maximum water in both the drainage channel and the canal causes the worst condition. Students often forget that the weight of the water inside the canal acts downwards, which actually counteracts the upward hydrostatic pressure of the drainage water and reduces the net uplift pressure.