Which of the following statements is correct in relation to the compaction of soil?

1. Relative compaction is the same as relative density.

2. Vibroflotation is effective in the case of highly cohesive soils.

3. 'Zero air void line' and 100% saturation line are identical.

Explanation:

Compaction of Soil

Compaction is a process used to densify soil, reducing its porosity and increasing its stability by mechanical means. It is crucial in construction to ensure a firm foundation, reduce settlement, and increase the load-bearing capacity of the soil.

Analyzing the Given Statements

1. "Relative compaction is the same as relative density." (Incorrect)

   • Relative compaction refers to the ratio of the field dry density of soil to the maximum dry density obtained in the laboratory, expressed as a percentage.

   • Relative density, on the other hand, is a measure of the compactness of granular soil, comparing the void ratio of a soil to its minimum and maximum void ratios.

2. "Vibroflotation is effective in the case of highly cohesive soils." (Incorrect)

   • Vibroflotation is a ground improvement technique used to densify granular soils, such as sands and gravels, by inserting a vibrating probe into the ground.

   • It is not effective for highly cohesive soils (clays and silts) as they do not allow the free movement of particles required for densification.

3. "'Zero air void line' and 100% saturation line are identical." (Correct)

   • The zero air void line represents the condition where the soil is fully saturated, meaning all voids within the soil are filled with water, leaving no air.

   • This line is also referred to as the 100% saturation line, as it indicates the theoretical maximum dry density of the soil for complete saturation.

Conclusion: Based on the analysis, Statement 3 is correct, and statements 1 and 2 are incorrect. Therefore, the correct answer is:

Option 3