Question

The unadjusted RMR of a tunnel roof is 64. A single joint set exists in the roof as shown in the figure. 

Using the abridged RMR table for adjustment orientation, the RMR is _______ (in integer)
 

Hint:

In RMR calculations, adjustments are made based on joint orientation. A joint dip between \( 20^\circ \) and \( 45^\circ \) typically results in a small negative adjustment when the tunnel is driven in the same direction as the joint dip.

Answer 1

Correct Answer: 54

The given values are: 
The unadjusted RMR of the tunnel roof is \( 64 \). 
The dip of the joint is \( 40^\circ \), which falls within the range of \( 20^\circ \) to \( 45^\circ \). 
The tunnel is driven in the direction with respect to the joint.
Step 1: Identifying the adjustment for joint dip. 
According to the RMR adjustment table:
For a joint dip between \( 20^\circ \) and \( 45^\circ \), the adjustment rating is \( -2 \) when the tunnel is driven with the dip.
Step 2: Adjustment for the orientation of the tunnel.
The tunnel is driven in the same direction as the joint dip, meaning the adjustment rating is \( -2 \). 
Step 3: Calculate the final RMR. To calculate the final RMR, we subtract the adjustment from the unadjusted RMR: \[ {Final RMR} = 64 - 2 - 8 = 54 \] Conclusion: The adjusted RMR of the tunnel roof is \( \mathbf{54} \).