How can concrete buttress stabilize rock fall?

Sometimes there is a cavity in rock slopes which is caused by previous rock falls. Concrete buttress, together with the use of rock dowels, could help to stabilize the rock slope.

The buttress serves to avoid local toppling of rock face. Moreover, it keeps protects the unstable rock and keep it in place. The presence of buttress also helps hold up the overhang. The size of buttress should be large enough to support the weak rock. In case the surface on which the buttress is founded is not normal to the resultant forces exerting on the buttress, buttress is tied to rock surface by using rock dowels to avoid the occurrence of sliding.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.