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GATE 2018 CE (CE2) – Question 43

Geotechnical Engineering · Permeability and seepage: flow nets, uplift pressure, piping, capillarity · 2 marks · Multiple choice

Three soil specimens, each 150 mm long and 100 mm diameter, are arranged in series in the constant-head apparatus shown. Screens keep them intact. Their respective permeabilities are 0.01, 0.003 and 0.03 cm/s. The indicated head h is ______.

Diagram for GATE 2018 CE (CE2) question 43
  1. 0 mm
  2. 40 mm
  3. 255 mm
  4. 560 mm

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Correct answer: (B) 40 mm

Explanation

Equal-area specimens in series carry the same flow. Head losses are proportional to $L/k$, giving ratio $100:333.333:33.333=3:10:1$. The total drop is 560 mm; the final specimen loses $560/14=40$ mm. Thus h = 40 mm (B).