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GATE 2026 MN – Question 22

Geomechanics and Ground Control · Geomechanics · 1 mark · Multiple choice

A500 g rock sample retains400 g after the two standard wetting/drying cycles of a slake-durability test. Find the Slake Durability Index in percent.

  1. 10
  2. 40
  3. 20
  4. 80

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Correct answer: (D) 80

Explanation

The index is the retained dry mass divided by the initial dry mass, multiplied by100. Thus SDI=400/500×100=80%, D. The20% mass lost is the complement, rather than the durability index itself.

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