Engineering Geology

Chapter 9
Figure 9.6
Dentition and rock bolts used to stabilize an excavation in limestone along the A55 road in North Wales.
the properties of the rock slope itself (by anchoring or bolting) than to remove the rock and
replace it with concrete.
Gunite or shotcrete frequently is used to preserve the integrity of a rock face by sealing the
surface and inhibiting the action of weathering (Fig. 9.7). They are pneumatically applied
mortar or concrete, respectively. Coatings may be reinforced with wire mesh and used in
combination with rock bolts. Heavily fractured rocks may be grouted in order to stabilize them.
Restraining structures control sliding by increasing the resistance to movement. They include
retaining walls, cribs, gabions and buttresses. There are certain limitations that must be considered
before retaining walls are used for slope control. These involve the ability of the structure
to resist shearing action, overturning and sliding on or below the base of the structure.
Retaining walls often are used where there is a lack of space for the full development
of a slope, such as along many roads and railways. As retaining walls are subjected to
unfavourable loading, a large wall width is necessary to increase slope stability. Reinforced
earth can be used for retaining earth slopes. Such a structure is flexible and so can accommodate
some settlement. Thus, reinforced earth can be used on poor ground where
conventional alternatives would require expensive foundations. Reinforced earth walls are
constructed by erecting a thin front skin at the face of the wall at the same time as the earth
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