Engineering Rock Mechanics

Questions 16.7- 76.7 0: rock reinforcement and rock support 467

Q 1 6.6 A long underground chamber is to
be constructed in a rock mass with frac-
tures dipping at 25" as shown. This prob-
lem is included in Goodman (1989).
(a) Assuming the friction angle of the
fractures, 4J, is 50", use the $, geomet-
rical construction in two dimensions to
locate zones of potential distress around
the opening.
= 20"
to investigate the effect of rock deterioration on interlayer slip around
the excavation.

(b) Repeat this procedure with

416.7 In a paper discussing the potential slip on fractures in the rock
around a tunnel or shaft, Daemen (1983) uses the solution for the stresses
around a circular opening in a CHILE rock to establish the normal and
shear stresses on the fractures. Applying the Mohr-Coulomb criterion
to these stresses enables the potential zones of distress around the
excavation to be established.

t^2 r/R

The zones of distress shown in Daemen's diagram above are for an

Show that the same result for the zone of distress at the excavation

isotropic stress field and an angle of friction of 4 = 20".

boundary can also be obtained using the 4j theory.

Q 16.8 Two types of 'ground response curve', A and B, are illustrated in
the diagram below. The curves indicate the amount of support pressure
required to maintain an excavated rock surface at a given value of
displacement.