Allied & ICAR Exam Bank • ALLIED_1230 MCQ • 1 Mark

Section 5: Irrigation and Drainage Engineering

Agricultural Drainage and Salinity

Subtopic: Subsurface Drain Envelopes

Question Statement:

A synthetic geotextile or graded gravel envelope is wrapped around corrugated perforated PVC subsurface drain pipes to:

Options:

  • (A) Prevent fine soil particles from migrating into and silting up the pipe while enhancing entrance permeability
  • (B) Completely prevent water from entering the drain
  • (C) Increase water pressure inside the pipe
  • (D) Act as an electrical insulator

Answer Key:

A

Step-by-Step Solution & Explanation

Drain envelopes function as a mechanical filter to retain unstable soil particles while simultaneously offering high permeability around perforations to reduce entrance head loss.
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