Rock slopes in civil and mining engineering

Rock slopes with heights approaching 1000 m are now being designed and excavated in various open pit mining and civil engineering projects around the world. The economic impact of excessively conservative designs or of failures in these slopes can be very large and every effort has to be made to optimise their design. Their size means that they will almost always contain a number of significant structural features and a variety of geological materials. The input required for these models includes a comprehensive geological data base that contains both structural geology and lithological information, an hydrogeological model that permits water pressures to be estimated throughout the slope, estimates of rock mass and discontinuity strength and deformation properties and an understanding of external forces, such as those due to earthquakes, that may be imposed on the slope. Site investigation techniques that can be used to obtain this information and the methods, that can be used to estimate rock discontinuity and mass properties, are reviewed in this paper. Developments in limit equilibrium and numerical modelling techniques are reviewed and their applicability to the design of these large slopes is presented. The importance of blasting control in the excavation of the slope is discussed. The use of drainage to improve the stability of the slopes is also considered. Monitoring the behaviour of the rock mass and the subsurface groundwater during construction and subsequent operation of the slope is an important component of rock slope engineering and these techniques are reviewed. Practical examples from large projects around the world are presented