# The Liquid Limit and Plastic Limit of sample are 40% and 30% respectively. If 20% of the soil is finer than 0.002 mm then the activity ratio of the so

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The Liquid Limit and Plastic Limit of sample are 40% and 30% respectively. If 20% of the soil is finer than 0.002 mm then the activity ratio of the soil sample would be:
1. 0.5
2. 1.0
3. 1.5
4. 2.0

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Correct Answer - Option 1 : 0.5

Explanation

The activity of the soil is defined as the ratio of plasticity index of the soil to the percentage of particles finer than 2μ or 0.002 mm.

${A_t} = \frac{{{I_P}}}{c}$

Ip = Plasticity index of the soil = LL - PL

LL = Liquid limit of the soil

PL = Plastic limit of the soil

Given,

LL = 40 %, PL = 30%

percentage of particles finer than 2μ or 0.002 mm (C) = 20%

Plasticity Index =  = 40 – 30 = 10%

∴ Activity = 10/20 = 0.5