Question

Consider the following statements related to pore pressure parameter \( A \), \( A_f \) (value of \( A \) at failure) and \( R \) (over consolidation ratio): (A) \( A_f \) is zero when \( R = 1 \)
(B) \( A_f \) is negative when \( R>4 \)
(C) \( A_f \) increases as \( R \) decreases
(D) \( A_f \) decreases as \( R \) decreases
Choose the most appropriate answer from the options given below:

• A. (A) and (C) only
• B. (A), (B) and (C) only
• C. (A), (B), (C) and (D)
• D. (B) and (D) only

Hint:

The pore pressure parameter \( A_f \) is zero when \( R = 1 \) and increases as \( R \) decreases.

Answer 1

The Correct Option is A

Step 1: Understanding the Relationship Between \( A_f \) and \( R \).
- (A) \( A_f \) is zero when \( R = 1 \): At \( R = 1 \), the soil is normally consolidated, and the value of the pore pressure parameter \( A_f \) is typically zero.
- (B) \( A_f \) is negative when \( R>4 \): This statement is incorrect. \( A_f \) is typically not negative when \( R>4 \).
- (C) \( A_f \) increases as \( R \) decreases: As the over-consolidation ratio \( R \) decreases, the pore pressure parameter \( A_f \) increases.
- (D) \( A_f \) decreases as \( R \) decreases: This statement is incorrect as \( A_f \) increases as \( R \) decreases.

Step 2: Conclusion.
Thus, the correct answer is (A) and (C) only, making option (1) the correct answer.

Final Answer: \[ \boxed{1. \, (A) \, \text{and} \, (C)} \]