Questions 20.7-20.70: design of underground excavations 4836~ = (56.20 - 3.304pA - 0.533~~) x
6c = (56.20 - 0.533pA - 3.304~~) x6A = (56.20 - 3.304~~ - 1.121pB - 0.533~~) x iop3
6s = (66.52 - 1.121pA - 3.602~~ - 1.121pC) x iop3
6c = (56.20 - 0.533~~ - 1.121pB - 3.304~~) x iw3.
Analysis of these geometries has been undertaken using a CHILE bound-
ary element program, in order to determine the relation between dis-
placement and support pressure at the various pillar locations. These
relations are given below the sketches with 6 representing displacement
and p representing support pressure.
The support pressure is to be supplied by the rock pillars. Perform
a rock-support interaction analysis for each of the two geometries in
order to determine which is the preferred design. The stress-strain
characteristics of the two pillars are as given below:
u (MPa) 5.0 8.0 10.0 11.1 11.4 10.9 10.0 8.7 3.0 0.5
E x 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 7.0 12.0Q20.6 A new mining operation is planned which can extract from one
of two coal seams. The first seam is at a depth of 250 m and has a
thickness of 3 m, and the second seam is at a depth of 500 m with a
thickness of 1 m. A preliminary design for the longwall mining panels
calls for the upper seam to be mined with a panel width of 200 m, and
the lower seam to have a panel width of 400 m (see the sketch below for
typical geometry, in which the mining direction is into the page).
Centreline Panel edge
It has been suggested that the Subsidence Engineers’ Handbook (SEH)
(National Coal Board, Mining Department, 1975) can be used to provide