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GATE 2016 CE (CE2) – Question 22

Geotechnical Engineering · Permeability and seepage: flow nets, uplift pressure, piping, capillarity · 1 mark · Multiple choice

The relationship between the specific gravity of sand (G) and the hydraulic gradient (i) to initiate quick condition in the sand layer having porosity of 30% is

  1. G = 0.7i + 1
  2. G = 1.43i − 1
  3. G = 1.43i + 1
  4. G = 0.7i − 1

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Correct answer: (C) G = 1.43i + 1

Explanation

Critical gradient is ic=(G−1)/(1+e). Since porosity n=e/(1+e)=0.30,1/(1+e)=1−n=0.70. Therefore i=0.70(G−1), or G=1+i/0.70≈1+1.43i. This is **C**.