346 Underground excavation instability mechanisms
Block 234Block 245Block 235Block 345419.2 For the unstable roof blocks established in the answer to
Q19.1, determine the direction of movement, and plane(s) of sliding
where relevant.A79.2 For each block which has been identified as being unstable due
to sliding, we need to identify the sliding direction. This will be the most
steeply __ dipping of
one of ihethree lines of intersection of two planes which make up
the faces of the block; or
the line of maximum dip of one of the planes which forms the block,
providing the line of maximum dip lies on the periphery of the spherical
triangZe fhat defines the block.
Identify and label each of the intersections shown on the projection,
and determine the orientation of each one. The intersections are as
follows: