Subtopic: Planning, design and layout of surface and sub-surface drainage systems
Question Statement:
In the design of agricultural subsurface relief drain pipe networks, what is the minimum recommended self-cleansing velocity required to prevent sediment siltation and clogging inside the pipe?
Options:
(A) $0.60 \text{ to } 0.75\text{ m/s}$
(B) $0.05 \text{ to } 0.10\text{ m/s}$
(C) $3.0 \text{ to } 4.5\text{ m/s}$
(D) $10.0\text{ m/s}$
Answer Key:
A
Step-by-Step Solution & Explanation
A minimum flow velocity of $0.60 \text{ to } 0.75\text{ m/s}$ under design flow conditions is required to maintain self-cleansing action, keeping fine sands and silt particles in turbulent suspension and conveying them to the outlet. Velocities below $0.4\text{ m/s}$ permit siltation. Option A is correct.