Mine Development & Surveying

Drilling Methods & Machines

Penetration rate and drilling time for a blast round, and the specific-drilling measure of drilling effort per unit rock.

PART 1

Topic Breakdown & Traps

The Engineering Principle

Rock is drilled by percussive, rotary or rotary-percussive machines; the key performance figure is the penetration rate (metres drilled per minute). The time to complete a round is the total drilled length divided by that rate. Specific drilling — metres of hole per cubic metre of rock broken — measures how drilling-intensive a blast pattern is, and is a useful cost indicator.

The Core Formula Matrix

Drilling time

= \frac{total drilled length}{penetration rate}

; total length

= N \times d

.

Specific drilling

= \frac{total drilled length}{volume of rock broken}

[m/m^{3}]

The ‘IIT Traps’

⚠
Total length = holes × depth. Forgetting to multiply by the number of holes badly under-counts drilling time.
⚠
Penetration rate divides, not multiplies. Time $=$ length $/$ rate.
⚠
Specific drilling is m per m³, not per tonne unless you convert through density.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

A drill advances at a penetration rate of

0.5 m/min

. The time to drill one

3 m

hole is:

Q2MEDIUM2 Marks · NAT

A round needs

20

holes, each

3 m

deep, drilled at

0.6 m/min

(ignore repositioning). The total drilling time is ______ min. (Round off to the nearest whole number.)

min

Q3HARD2 Marks · NAT

If those

60 m

of drilling break

200 m^{3}

of rock, the specific drilling is ______ m/m³. (Round off to two decimal places.)

m/m³