Question

From laboratory investigations, the liquid limit, plastic limit, natural moisture content and flow index of a soil specimen are obtained as 60%, 27%, 32% and 27, respectively. The corresponding toughness index and liquidity index of the soil specimen, respectively, are
1. 0.19 and 6.60
2. 6.60 and 0.19
3. 0.15 and 1.22
4. 1.22 and 0.15

Answer 1

Correct Answer - Option 4 : 1.22 and 0.15

Explanation

we know, 

a) Toughness Index: Toughness index is defined as the ratio of plasticity index (I_P) of the soil to the flow index (I_F) of the soil.

The toughness index varies between 0 to 3.

Given,

Liquid Limit (LL) = 60 %, Plastic Limit (PL) = 27%, Water content (w) = 32 %, and Flow indx (If) = 27

 Plasticity Index (PI) = LL - PL = 60 - 27 = 33% 

\(\begin{array}{l} Toughess\;index = \frac{{Plasticity\;index}}{{Flow\;index}}\\ \end{array}\)

Toughness index = 33/27

∴ Toughness index = 1.22

b) Liquidity Index

The Liquidity Index, IL­ is given as:

\({I_L} = \frac{{{W_n} - \;{PL}}}{{{LL} - \;{PL}}}\)

Where,

 LL - PL = Plasticity Index

\({I_L} = \frac{{{32}\ - \;{27}}}{{{60} - \;{27}}}\) = 5/33 = 0.1515

∴  Liquidity Index is 0.15