Análise geologico-geotécnica e otimização de suporte em mineração subterrânea

Abstract

The increasing demand for mineral resources over time has led to a need for adaptation in exploration methods, transitioning from surface to subsurface mining as surface reserves become depleted. Underground excavations in rock masses require a support and containment system, designed based on a geomechanical classification system. The geomechanical design of an underground mine is crucial, considering the unique characteristics of each mine. Characterizing the rock mass using only intact rock strength properties is insufficient for proper support design, as structural features and their properties must also be considered. Therefore, a kinematic analysis of interactions between discontinuity families intercepted by each excavation is essential. In this context, this study presents a case study at the Crixás-GO Underground Mine, aiming to characterize the rock mass and size the support for development galleries based on planned geometry, depth, orientation, and dip of the excavation axis. This indepth study is justified by the need to maximize economic outcomes and reduce risks associated with subsurface exploration, using a kinematic block analysis method through the development of three-dimensional models. The results of this research reflect a thorough analysis based on data provided by the partnering company, focusing on both temporary and permanent galleries. The support adopted for temporary galleries was split-sets, while for permanent galleries, resingrouted rock bolts and MD Bolts were used, with the latter examined due to its similarities to resin-grouted bolts. Detailed information on discontinuities proved crucial for understanding the rock mass behavior. The software employed utilizes this information to create joint combinations, generating blocks and assessing their interaction with galleries. Algorithms are applied to divide the rock mass into blocks, considering the provided characteristics. These blocks represented potential wedges susceptible to sliding, involving a comparative analysis of shear forces and available strengths. Pre-existing models were generated, considering a temporary gallery with a trend of 325° and permanent galleries in eight different directions, each adding 22.5°, with a fixed plunge of 7°. Considering critical directions emphasizes the importance of evaluating stability in various orientations. The established safety factor was 1.2, indicating an adequate safety margin for the analyzed galleries.