Many authors have been proposed several correlation equations between geomechanical classifications and strength parameters. However, these correlation equations have been based in rock masses with different characteristics when compared to Brazilian rock masses. This paper aims to study the applicability of the geomechanical classifications to obtain strength parameters of three Brazilian rock masses. Four classification systems have been used; the Rock Mass Rating (RMR), the Rock Mass Quality (Q), the Geological Strength Index (GSI) and the Rock Mass Index (RMi). A strong rock mass and two soft rock masses with different degrees of weathering located in the cities of Ouro Preto and Mariana, Brazil; were selected for the study. Correlation equations were used to estimate the strength properties of these rock masses. However, such correlations do not always provide compatible results with the rock mass behavior. For the calibration of the strength values obtained through the use of classification systems, stability analyses of failures in these rock masses have been done. After calibration of these parameters, the applicability of the various correlation equations found in the literature have been discussed. According to the results presented in this paper, some of these equations are not suitable for the studied rock masses.
This article presents an approach to rockfall hazard assessment for rocky slopes based on a previously published rockfall hazard methodology. The original method is appropriate to high alpine rocky slopes exposed to large scale deformations. It evaluates the parameters related to the geomechanical characterization of rock mass, indications of activity, external influences and event intensity. The original methodology was modified to consider different contexts, including geological, climatic and social environments. Parameters related to external influences were modified; the geometry and characteristics of the slope and the catchment area were introduced. The original methodology and the new proposal were applied to two urban slopes and one railway slope in order to test and compare the methods. The original proposal could not represent the rockfall conditions of these slopes. The new proposal was validated using two mine slopes, whose conditions of stability are known. The results of the analyses with the urban slope and the railway slope were coherent with the situation observed at the field. The validation in the mine slopes showed that this approach is applicable in several situations, being able to determine how hazardous a slope is in relation to rockfall events.
Câmaras e Pilares é um método de lavra subterrânea em que são deixados pilares do próprio bem mineral sustentando o teto. No presente trabalho é simulada uma lavra de carvão em Câmaras e Pilares. A maioria dos equacionamentos de resistência de pilares de carvão considera apenas a resistência do carvão e a relação entre a largura e a altura do pilar. Na literatura técnica existem equações de dimensionamento do pilar que consideram os parâmetros elásticos das encaixantes que formam o teto e o piso. Nas simulações numéricas, foi considerado um arenito no teto e um siltito no piso. Simulações foram realizadas com o uso de elementos finitos de interface no contato entre o carvão e as encaixantes. O programa de elementos finitos Adonis foi utilizado nas simulações. Os dados geotécnicos da Camada Bonito da Região Carbonífera de Santa Catarina foram tomados como referência. As condições de simetria do problema foram estudadas. Os modelos que consideram elementos de interface se mostraram sensíveis ao valor da rigidez tangencial na distribuição de tensões do contato entre pilar e encaixantes. A rigidez relativa das encaixantes influencia na distribuição de tensões entre pilar e encaixantes. Estas questões poderiam ser consideradas no dimensionamento de pilares.
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