Marble - Colorado Geological Survey

1. Open Quarry: 3,260,000 cf = 285,250 tons
APPENDIX F
Calculations
Minable Reserves
2. Underground extention of open quarry gray
Lower falls unit.
Extraction ratio R-1- [(FXS)l/(cp)]
F = safety factor say 5;
S = applied stress = 200 ft x 62.4 x 2.6 x 1/144 = 225 psi
C = compressive stength 82 1/0 psi
R = 1- [(5X225X1/8240)] = 86%, say 80%
Minable reserve = .80 x 500 ft x 500 ft x 65 ft x 13,000,000 cf
13,000,000 x 175 x y2000 = 1,137,500 tons
3. Underground at south property white marble leave a layer of white marble below
hornfels: L - [(2t2 x Oe)/W)].5
Where L = length of span, say 50 ft
t = thickness of beam in the back
Oe = allowable working stress, modulus of rupture divided by safety factor
W = uniform load
Modulus of rupture/ SF = Oe = 1200/2 = 600 psi
Uniform load = 200 psf/Hn ft
Say span = 50 ft 50 2 = 2t 2 x 600 x 1/200
t - 20 ft thickness of layer
Reserve is 100 ft thick - 20 ft = 80 ft remaining
pillars at W/H = 1, 20% required
Minable reserve = 80 ft x 725 ft x 400 ft x .80 = 18,560,000
18,560,000 cf x 175 x 1/2000 =1,624,000
Total minable reserve = 34,820,000 cf or 3,046,750 tons