Question

Consider the following statements:
1. Standard penetration test is commonly used for cohesionless soils.
2. Standard penetration test results in respect of a cohesionless soil are correlated to its density index and friction angle.
3. Use of N-value not corrected for overburden pressure leads to highly conservative design of footings at shallow depths.
Which of these statements are correct?

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

Answer 1

The correct option is A 1, 2 and 3

The N-value in a granular soil is influenced by the over burden pressure. If two granular soil possesing the same relative density but having different confining pressure are tested, one with a higher confining pressure gives a higher N value. Since the confining pressure increases with depth, the N values at shallow depths are underestimated and the N values at larger depths are overestimated.