PERMFILE100116

• Permit No: C1981038
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: VOLUME 2 MINE PLANNING APPENDIX - PILLAR STABILITY
• Media Type: D
• Archive: No

EXAMPLE
1) Desired pillar size - 100' X 100'
2) Desired center to center entry dimensions - 120' X 120'
3) Maximum overburden depth - 1200'
• Assumptions:
p = pillar width = 100'
1 = pillar lenyth = 100'
m = mining height = 13'
H = overburden depth = 1200'
X = density of overburden = 1.1 psi/ft. depth = 158 lb/ft3
~ = anyle of internal friction = 40°
Tan 6=1+Sin~
1 - Sin ~
Cohesion = Uniaxial Strength (after Abel)
2 Tan B
T,A.L. = tributary area load (maximum load to be carried by one pillar)
_ (p + 20)(1 + 20) (~ )(H)
2000
00 =compression strength (psi) at pillar ribside or cohesion strenyth
• = 600 ps i
off =horizontal pressure (psi)
_ [6.944 X 10'3 (X )(H)]
o„ =maximum stable vertical pillar stress (psi)
_ (oH Ta n B + oo )
Y = distance into pillar at location of maximum stable pillar stress (ft .),
or to edge of confined core
= m In o„
Tan B (Tan B-1) o0
L = load carrying capacity of pillars (after Abel)
= 7,2 X lU-2 ov [Pl - PY - lY + 4 Y2)]
3
(for rectangular pillars where 2 Y <P)
= 7.2 X lU-2 Oy [P2 - 2 PY + 4 Y2]
3
• (for square pillars where 2Y <P)
Safety Factor = L
T.A.L.