Question

A multi-point borehole extensometer is used to monitor

• A. Convergence between the roof and the floor
• B. Strain between fixed points along a borehole
• C. Strain between the anchor point and the reference point on the surface
• D. Changing distances between fixed points along a borehole

Hint:

A multi-point borehole extensometer measures \[ \boxed{ \text{Internal rock displacement at different depths.} } \]

Answer 1

The Correct Option is D

Step 1: Recall the purpose of a borehole extensometer. A borehole extensometer is an instrument used to measure displacement occurring within a rock mass.

Step 2: Identify the quantity measured. A multi-point borehole extensometer measures the relative movement between several anchor points installed at different depths in a borehole. Thus, it monitors \[ \boxed{\text{Changing distances between fixed points along a borehole}.} \] Therefore, \[ \boxed{(D)} \] is the correct answer.