Mining Methods & Machinery

Longwall Mining (Face Output)

Output per shearer cycle from face length, web and seam height, scaled up to daily and annual production.

PART 1

Topic Breakdown & Traps

The Engineering Principle

In longwall mining a shearer traverses a long face, taking a slice (the web) of the seam each pass. The coal won per cycle is the face length times the web depth times the seam height times the coal density. Multiplying by the number of cycles per day and the working days per year gives daily and annual output. Longwall delivers high, concentrated production.

The Core Formula Matrix

Output per cycle:

P_{cy c l e} = L \times d \times h \times ρ

L

= face length,

d

= web depth,

h

= seam height,

ρ

= coal density.

Daily:

P_{d a y} = P_{cy c l e} \times (cycles/day)

. Annual:

P_{y e a r} = P_{d a y} \times (working days)

The ‘IIT Traps’

⚠
Web is the cut depth per pass, typically 0.6–1.0 m — not the seam height.
⚠
Multiply by density to convert mined volume to tonnes.
⚠
Annual output uses working days (with availability), not 365.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

200 m

face,

0.8 m

web,

2 m

seam, coal density

1.4 t/m^{3}

. Output per cycle is:

Q2MEDIUM2 Marks · NAT

If that face completes

10

cycles per day, the daily output is ______ tonnes. (Round off to the nearest whole number.)

t/day

Q3HARD2 Marks · NAT

Over

300

working days, the annual output is ______ Mt. (Round off to two decimal places.)

Mt/yr