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GATE 2016 CE (CE2) – Question 23

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

The results of a consolidation test on an undisturbed soil, sampled at a depth of 10 m below the ground level are as follows: Saturated unit weight : 16 kN/m3 Pre-consolidation pressure : 90 kPa The water table was encountered at the ground level. Assuming the unit weight of water as 10 kN/m3, the over-consolidation ratio of the soil is

  1. 0.67
  2. 1.50
  3. 1.77
  4. 2.00

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Correct answer: (B) 1.50

Explanation

The water table is at ground level, so effective unit weight is16−10=6kN/m³. At10m, present effective vertical stress is60kPa. OCR equals preconsolidation stress divided by present effective stress:90/60=**1.50, B**. Using total stress would give an incorrect ratio.