Q42
What does the term "overbreak" refer to in tunnel development?
A.
A large raise
B.
Excess rock excavation beyond design limits
AnswerC.
Equipment failure in drift
D.
Poor blasting pattern
Answer: Option B
Solution
Answer: Option B
Solution:
Overbreak is unintentional excavation beyond the tunnel design profile.The correct answer is: Excess rock excavation beyond design limitsIt leads to extra ground support costs and instability.Caused by over-blasting or weak rock zones.