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GATE 2021 CE (CE1) – Question 17

Geotechnical Engineering · Compaction and one-dimensional consolidation · 1 mark · Multiple choice

Saturated clay in an oedometer is at equilibrium under 50 kN/m² vertical pressure. Immediately after increasing the pressure to 150 kN/m², the effective stress and pore water pressure respectively are

  1. 150 kN/m² and 0
  2. 100 kN/m² and 50 kN/m²
  3. 50 kN/m² and 100 kN/m²
  4. 0 and 150 kN/m²

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Show answer and explanation

Correct answer: (C) 50 kN/m² and 100 kN/m²

Explanation

Immediately after loading, drainage has not occurred and the added 100 kPa is carried by excess pore pressure. The pre-existing effective stress remains 50 kPa, while pore pressure becomes 100 kPa. Their sum is the new total stress, 150 kPa. **Answer: C**.