Subtopic: Planning, design and layout of surface and sub-surface drainage systems
Question Statement:
Modified Hooghoudt’s equation for the computation of drain spacing is applicable to
Options:
(A) homogeneous soils
(B) anisotropic soils
(C) heavy clay soils only
(D) layered soils
Official Answer Key:
D
Step-by-Step Solution & Explanation
• Hooghoudt’s original steady-state drain-spacing equation assumes a homogeneous profile above an impermeable layer. The modified Hooghoudt equation introduces an “equivalent depth” concept precisely to extend the method to soil profiles composed of distinct layers with different hydraulic conductivities.
• Final Answer: (D) layered soils
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