356 Underground excavation instability mechanisms
Block 234 Block^235Block 245 Block 345Block Stability condition Direction
123
124 slides along intersection of sets 1 and 2 119134
125 slides along intersection of sets 1 and 2 119134
134 Q58/54
135 Q58/54
145
234 127181
235 127181
245
345 slides along intersection of sets 3 and 5 044137slides along line of maximum dip of set 3 127182slides along line of maximum dip of set 1
slides along line of maximum dip of set 1
stable (no part of the block dips in excess of the friction angle)slides along line of maximum dip of set 3
stable (no part of the block dips in excess of the friction angle)slides along he of maximum dip of set 3Q19.6 For both the haunch A and the side wall B studied in Qs 19.4
and 19.5, and with the information given in Q19.1, calculate the
factor of safety of the block formed by fracture sets 1,2 and 5.A 19.6 In the south east haunch of the excavation, block 125 suffers from
sliding along the line of maximum dip of fractures from set 5 (i.e. in