Correct Answer - Option 3 : -0.24
Concept:
The plasticity Index, IP of soil is given as:
IP = WL - Wp
The Liquidity Index, IL is given as:
\(({I_L} = \frac{{{W_n} - \;{W_P}}}{{{W_L} - \;{W_P}}} = \frac{{{W_n} - \;{W_P}}}{{{I_P} }})\)
Where
WL is the liquid limit of soil
WP is the Plastic Limit of soil
⇒ IP is plasticity Index = Liquid Limit - Plastic Limit
Wn is water content of the soil under given conditions or natural water content
Calculation
Given: WL = 90%; IP = 50 %
Natural Water Content Wn = 28%
IP = WL - Wp ⇒ 50 = 90 – Wp ⇒ Wp = 40 %
The Liquidity Index, IL is calculated as:
\(({I_L} = \frac{{28 - \;40}}{{50}})\) = - 0.24
1. The Liquidity index of soil indicates its degree of consistency i.e. Higher the liquidity index, the more the soil will be consistent.
2. If IL ≥ 1, then soil is in liquid state.
3. If IL = 0, then the soil is in the plastic state.