The GATE Grind

GATE 2021 CE (CE1) – Question 18

Geotechnical Engineering · Three-phase system, phase relationships, index properties and soil classification · 1 mark · Multiple choice

A partially saturated soil has water content 25%, bulk unit weight 18.5 kN/m³ and specific gravity 2.65. With water unit weight 9.81 kN/m³, its unit weight on full saturation is

  1. 21.12 kN/m³
  2. 19.03 kN/m³
  3. 20.12 kN/m³
  4. 18.50 kN/m³

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) 19.03 kN/m³

Explanation

Dry unit weight is $18.5/1.25=14.8$ kN/m³. From $\gamma_d=G_s\gamma_w/(1+e)$, $e=2.65(9.81)/14.8-1=0.75652$. Thus $\gamma_{sat}=(G_s+e)\gamma_w/(1+e)=19.0251$ kN/m³, giving **19.03 (B)**.