Engineering Rock Mechanics

350 Underground excavation instobilify rnechonisrns

h = $14 tan814 + 145 tan845 + 151 tan8511

= i(6. tan 27 + 75 e tan 2 + 3. tan 50)

= i(3.0 + 2.6 + 3.6) = 3.1 nun = 0.61 m

W = iy Ajh = f x 22 x 10.62 x 0.61 = 47.5 kN, and

p =fyh=i x 22 x 0.61 = 4.5 kN/m2.

Angles taken from the hemispher-

ical projection:

823 = la2 - a31 = 1195 - 1271 = 68

e35 = la3 - a51 = 1127 - 3351 = 208

eS2 = la5 -a21 = 1335 - 1951 = 140

835 = 37

823 = 70

852 = 39

Block 235

Scale drawing of block (original scale 5 mm: 1 m):

Af = t(312131 sin8231 + $13151 sin8351 + +15121 sin8521)

= i(3 -44.60 - I sin681 + $ e 60.87. 1 sin2081 + $ - 87 I 44 I sin 1401)

= t(1223.9 + 1225.3 + 1230.3) = 1226.5 nun2 49.06 m2