140 Rock masses: deformobili?., strength and failuredifficulty of obtaining detailed information, simplified approaches have
been adopted.
The use of rock mass classification methods for evaluating rock mass
modulus (Q and A8.4), and the rock mass strength (Q and A8.9) can
provide good estimates. However, it is important to understand the
factors that govern rock mass deformability and strength in order to be
able to assess the validity of these simplified approaches in a given prac-
tical situation. We have highlighted this understanding in the questions
and answers in this chapter.
A further point is what happens to the rock mass after its strength has
been reached? The principles outlined in Section 6.1, A6.1 and A6.6 for
intact rock also apply to rock masses. Whether the rock mass failure will
be abrupt or progressive depends critically on whether it is being loaded
by a 'soft' or 'stiff' system.