Mining Methods & Machinery

Thick-Seam Mining (Recovery)

Recovery as the fraction of seam thickness extracted, in-situ versus recovered tonnage, and top-coal caving recovery.

PART 1

Topic Breakdown & Traps

The Engineering Principle

Thick seams cannot be taken in one lift, so methods (slicing, top-coal caving) recover only part of the seam. Recovery is the extracted thickness (or tonnage) over the in-situ total. In longwall top-coal caving (LTCC) the lower slice is cut directly while the top coal is caved and drawn at a lower recovery — the overall recovery combines both.

The Core Formula Matrix

Recovery:

R = \frac{extracted}{in-situ}

(thickness or tonnage).

Recovered tonnage:

T = (thickness \times area \times ρ) \times R

.

LTCC effective thickness:

h_{e f f} = h_{c u t} + h_{t o p} \times R_{t o p}

The ‘IIT Traps’

⚠
Recovery ≤ 100 %. A value above 1 means you flipped the ratio.
⚠
In-situ tonnage uses the *full* seam thickness; apply recovery afterwards.
⚠
In caving, only the top coal carries the reduced recovery — the cut slice is fully won.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

A method extracts

6 m

from an

8 m

seam. The recovery is:

Q2MEDIUM2 Marks · NAT

10 m

seam over

100, 000 m^{2}

(density

1.5 t/m^{3}

) is mined at

70%

recovery. The recovered tonnage is ______ Mt. (Round off to two decimal places.)

Q3HARD2 Marks · NAT

In LTCC, a

3 m

lower slice is cut directly and the

5 m

top coal is caved at

80%

recovery (total seam

8 m

). The overall recovery is ______ %. (Round off to two decimal places.)