Engineering Rock Mechanics

389

c v) 0.0

Notice that the strain profile is drawn using the sign convention given in

the SEH, which is tension positive.

50.0 100.0 150.0 200.0 250.0 300.0

1

-2.5E-3

Width of panel = 400 m, depth of panel = 500 m, seam thickness = 1 m
As the ratio of maximum subsidence to extraction thickness is about
0.75, for an extraction thickness of 1 m the maximum subsidence will
now be about 0.72 m. Using a multiplier for distances of 500 m, the
subsidence profile is given by the values in the table below, and is shown
in the diagram following. Notice from the diagram that, above the panel
edge, the subsidence is greater than 0.5 m, and that the overall width of
the subsidence trough is now more than 1000 m.

Subsidence (m) 2.138 2.025 1.800 1.575 1.350 1.125 0.900 0.675 0.450 0.225 0.000

Distance (m) 20.0 25.0 42.5 50.0 62.5 72.5 80.0 95.0 105.0 155.0 277.5

distance from panel centre line, m

0 100 200 300 400 500 600

0

0.8 - ~~~~~~~~~~~ ~~~~~~~~