ABSTRACT
Weak rock has an unconfined compressive strength (UCS) of between 1.25 and 5MPa. The general characteristics of weak rock mean that it is often unsuitable for engineering construction where it is required to offer a foundation support capability or a self-support capability in the long term when exposed not only to deforming pressures but also to groundwater and atmospheric effects. On the other hand, it can be excavated with relatively little effort. It represents a large percentage of exposed rock material on the earth's crust and has been the cause of several notable civil engineering failures.
