Question

Consider the following statements:
1. A differential free swell value of 40% indicates a soil with a high degree of expansiveness.
2. A swelling pressure of less than $20kN/m^2$ is not of much consequence.
3. The swelling pressure is a unique parameter for a swelling soil and is not influenced by other factors.
Which of these statements is/are correct?

• A. 1, 2 and 3
• B. 1 and 2 only
• C. 2 and 3 only
• D. 1 only

Answer 1

The correct option is B 1 and 2 only

Degree of expansiveness and differential free swell are tabulated below:
$\begin{array}{cc}\text{Degree of swelling}& \text{DFS percent}\\ \text{Low}& \text{< 20}\\ \text{Moderate}& \text{20 to 35}\\ \text{High}& \text{35 to 50}\\ \text{Very high}& \text{> 50}\end{array}$
The swelling pressure is not a unique parameter for a swelling soil. It is significantly influenced by several factors, the more important of them being the initial moisture content (moulding water content for remoulded soils), initial dry density, method of compaction, confining surcharge and the height of the soil specimen. For a given dry density, lower the initial moisture content, greater the water thirst and higher the swelling pressure.