Q154
What determines the need for secondary support in underground mines?
A.
Support material quality
B.
Lighting arrangement
C.
Primary support effectiveness
AnswerD.
Air velocity
Answer: Option C
Solution
Answer: Option C
Solution:
Secondary support supplements primary systems when they are insufficient.The correct answer is: Primary support effectivenessFactors like convergence or new cracks may trigger need.Includes cable bolts, retimbering, etc.