Mine Development & Surveying

Underground Drivages

The drill–blast cycle of a development heading — advance per round, number of rounds, and the muck produced.

PART 1

Topic Breakdown & Traps

The Engineering Principle

A development heading advances by repeating a drill–blast–muck cycle. Each round drills holes to a set depth, but the blast never pulls the full depth — the pull efficiency gives the actual advance per round. The number of rounds to drive a given length is the length divided by the advance, and the muck produced per round is the cross-sectional area times the advance times the rock density.

The Core Formula Matrix

Advance per round:

a = d η_{p u l l}

(

d

= hole depth,

η_{p u l l}

= pull efficiency).

**Rounds for a drive of length

L

**:

N = \frac{L}{a}

.

Muck per round (tonnes):

T = A a ρ

(

A

= cross-section,

ρ

= density).

The ‘IIT Traps’

⚠
Pull efficiency < 100%. The advance is always less than the hole depth; using the full depth over-states progress.
⚠
Muck uses the *advance*, not the hole depth. Only the blasted-out length contributes to the round's tonnage.
⚠
Round up the number of rounds. A fractional round still needs a full cycle.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

Holes are drilled to

2.0 m

depth with a pull efficiency of

80%

. The advance per round is:

Q2MEDIUM2 Marks · NAT

With an advance of

1.6 m

per round, the number of rounds required to drive a heading

120 m

long is ______. (Round off to the nearest whole number.)

Q3HARD2 Marks · NAT

A heading of cross-section

12 m^{2}

advances

1.6 m

per round in rock of density

2.5 t/m^{3}

. The muck produced per round is ______ t. (Round off to two decimal places.)