Question

Consider the following statements:
1. ‘Relative compaction’ is not the same as ‘relative density’.
2. Vibroflotation is not effective in the case of highly cohesive soils.
3. ‘Zero air void line’ and ‘100\% saturation line’ are not identical.
Of these statements:

• A. 1 and 2 are correct
• B. 1 and 3 are correct
• C. 2 and 3 are correct
• D. 3 alone is correct

Hint:

- Use Relative Density for granular soils and Relative Compaction for field density comparisons. - Vibroflotation is ineffective for cohesive soils. - ZAVL and 100% Saturation Line are not identical due to air voids and compaction effects.

Answer 1

The Correct Option is C

Step 1: Understanding the concept of Relative Compaction vs. Relative Density. - Relative Compaction is the ratio of field dry density to laboratory maximum dry density, expressed as a percentage. - Relative Density applies to coarse-grained soils, comparing void ratios. - However, the terms are sometimes used interchangeably in engineering practice. 
Step 2: Effectiveness of Vibroflotation. - Vibroflotation is a deep compaction technique effective for granular soils. - It is not effective for highly cohesive soils, as they resist vibration. 
Step 3: Understanding Zero Air Void Line vs. 100\% Saturation Line. - The Zero Air Void Line (ZAVL) represents maximum dry density achievable with full saturation (no air). - The 100% Saturation Line considers theoretical conditions. - Both are not identical because air content and compaction energy vary. 
Step 4: Evaluating the Statements. - Statement 1 is debatable due to engineering usage. - Statement 2 is correct (Vibroflotation is ineffective for cohesive soils). - Statement 3 is correct (ZAVL and 100% Saturation Line differ). Thus, the correct answer is (C) 2 and 3 are correct.