Question

If the liquid limit of soil is 25%, plastic limit is 15% and flow index is 12.5%, then its toughness index is:
1. 50%
2. 60%
3. 70%
4. 80%

Answer 1

Correct Answer - Option 4 : 80%

Concept:

Toughness Index: Toughness index is defined as the ratio of plasticity index (IP) of the soil to the flow index (IF) of the soil.

The toughness index varies between 0 to 3.

Calculation

Given

 Liquid Limit = 25%, plastic Limit = 15 %, Flow index = 12.5 %

 Plasticity Index = 25 - 15 = 10 % = 0.1

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

Toughness index = 0.1/0.125

Toughness index = 0.8 = 80%