UNSTABLE ROCK AND ITS TREATMENT SNOWY MOUNTAINS SCHEME
4. Where the rock mass has some well defined planar weak structure the bolting pattern should be oriented to take the weakness into account. For example bolts would be oriented normal to weak bedding plane or slabby joints forming the wall of an excavation. In most other cases, for example, where three sets of joints occur, dividing the rock mass into blocks, it is best to adopt a regular pattern, ignoring local variations in jointing, with bolts normal to the surface of the excavation. Steel channels spanning between bolts or wire mesh attached to bolts may be used to control fallout between bolts (Fig. 10).
The gravel is stabilized by model rock bolts and provided the ratio
length of bolts
spacing of bolts
is not less than 2, and the ratio
spacing of bolts
diameter of gravel
is not less than about 6.
(a) the ratio
length of bolts
spacing of bolts
(b) the ratio
length of bolts
spacing of bolts