Questions 16.1 -1 6.1 0:
rock reinforcement and
rock support
Q 16. I When rockbolts are used for
surface or underground excavations
to reinforce a fractured rock mass,
the rockbolts will be subjected to ten-
sion, shear and compressive forces.
The diagram below (from Windsor,
1997) indicates the types of forces on
rockbolts a to f.
Recognizing that rockbolts are de-
signed to operate in tension with little
shear force applied, rate these rock-
bolt configurations in terms of their
suitability on this criterion alone.
bCfQ 16.2 A rock block of weight W is bolted to a plane inclined at angle a to
the horizontal. Develop an expression for the bolt tension, T, in terms of
the angle, j3, at which the bolt is installed relative to the plane, the angle of
inclination of the plane and the Mohr-Coulomb friction properties, c and
4, of the block/plane interface. Hence, by differentiation, find the rockbolt
angle at which the bolt tension is minimized.
What is this angle,P, such that the
tension in the rockbolt is
minimized?Wsin416.3 The sketch below shows a rock block resting on a slope and
subject to a stabilizing force from a rockbolt. The strength of the interface
between the block and the slope is purely frictional, with an angle of
friction d.