New practical evaluation on mining rock slope stability

Dangerous areas near slopes occupied illegally by urban expansion is a complex social problem in several parts of the world. Many accidents have occurred in Brazil with loss of lives and a significant number of properties damages. This situation repeats every year and it is aggravated dramatically during heavy rain falls. Consequently a great number of studies were conducted to examine more accurately the question of the safety factor (SF) usually considered for rock slope engineering. The classical way of analysis describes as the ratio of the total resisting forces active against slopes sliding to the total forces tending to induce sliding, that is easily applied for some well defined discontinuous features. But this is not true for slopes with boulders, weathered rocks mixed by soils, or other complex rock mass structures. The fundamental question is to known if the present safety factor could be considered acceptable or if not what steps would be necessary for achieve safer results. Open pit mining brings a very similar situation due to its dynamic activities that require high steep slopes and constant change in their shapes for balancing between economical and safe operations. The results experienced from a hundred of natural and excavated slopes that have collapsed or are in critical condition were analyzed. A criteria for stability analysis and its potential application for mining operation is suggested.