Question

Identify the active support, out of support categories given for an underground coal mine

• A. Wire mesh
• B. Shotcrete
• C. Timber prop
• D. Hydraulic prop

Hint:

Examples of active support include \[ \boxed{\text{Hydraulic props and rock bolts (prestressed).}} \]

Answer 1

The Correct Option is D

Step 1: Recall the types of mine supports. Mine supports are broadly classified as: \[ \begin{aligned} \text{Active supports} &\rightarrow \text{Apply load to the rock mass before movement occurs.} \text{Passive supports} &\rightarrow \text{Provide resistance only after rock movement begins.} \end{aligned} \]

Step 2: Identify the active support. Hydraulic props provide continuous support by exerting active pressure on the roof, whereas wire mesh, shotcrete, and timber props mainly act as passive supports. Hence, \[ \boxed{\text{Hydraulic prop}} \] is the correct answer. Therefore, \[ \boxed{(D)} \] is the correct answer.