Question

If the rock has RMR value \(72\), then what will be its roof classification?

• A. Poor
• B. Fair
• C. Good
• D. Very good

Hint:

Remember the RMR classes: \[ \boxed{ \begin{aligned} 81-100 &\rightarrow \text{Very Good} 61-80 &\rightarrow \text{Good} 41-60 &\rightarrow \text{Fair} 21-40 &\rightarrow \text{Poor} <20 &\rightarrow \text{Very Poor} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Recall the Rock Mass Rating (RMR) classification. According to Bieniawski's RMR system, \[ \begin{array}{|c|c|} \hline RMR Range & Rock Mass Quality \hline 81-100 & \text{Very Good} 61-80 & \text{Good} 41-60 & \text{Fair} 21-40 & \text{Poor} \hline \end{array} \]

Step 2: Identify the classification. Since \[ 72 \in (61,80), \] the rock mass belongs to the \[ \boxed{\text{Good}} \] category. Therefore, \[ \boxed{(C)} \] is the correct answer.