TABLE OF CONTENTS In the previous chapter on excavation principles, we discussed the idea of taking the rock into the post-peak region of the complete stress-strain curve for excavation. Here, we discuss the principles of stabilization whether for staying in the pre-peak region, or for allowing the rock to pass into the post-peak region and utilizing its residual strength.
Following the introduction on the form of the disturbances caused by the excavation process, we discuss the two fundamental methods of stabilization: rock reinforcement and rock support. In each case, the behaviour of essentially continuous and discontinuous rock masses is discussed separately. Finally, we consider the principles of stabilization when the rock mass behaviour has attributes of both a continuum and a discontinuum (e.g. slip on planes of weakness). These principles are amplified and their practical application illustrated in the later chapters dealing with rock engineering.
There are two aspects of rock excavation that we will concentrate on here. The first is that one cannot prevent all displacements at the excavation boundary . The second is that a mistake in excavation design can be a major problem . In order to understand the displacements and avoid problems, we will consider the three primary effects of excavation and then decide on the ramifications for stabilizing excavations of all kinds.
The three primary effects of excavation are:
displacements occur because stressed rock has been removed, allowing the remaining rock to move (due to unloading);
there are no...
