Andre Cezar Zingano

Simulation — An Approach to Risk Analysis in Coal Mining

Traditional mine planning based on block models built with interpolation techniques such as kriging does not take into account the uncertainty associated with the estimates. These models are inadequate for short-range mine planning. In contrast, conditionally simulated models reproduce the actual variability (histogram) and spatial continuity (variogram) of the attributes of interest. Conditional simulation can be used to address the problem of measuring the uncertainty associated with an estimate. This paper outlines how the sequential Gaussian conditional simulation algorithm can be used to assess uncertainty of grade estimates and also illustrates how simulated models can be incorporated into mine planning and scheduling. A case study demonstrates the efficiency of the method in assessing risk associated with geological and engineering variables.

Slope stability analysis at highway BR-153 using numerical models

An existing cut slope on Highway RS-471/BR-153 is studied. The slope is composed of the Serra Geral Formations material: a highly altered volcanic breccia and above it a slightly altered and very fractured rhyolite. A numerical analysis of the slope is carried out in two dimensions. Fracturing of the rhyolite necessitates the use of a constitutive model for materials with families of discontinuities (Ubiquitous-joint). To simplify the analysis of the problem and to examine some of the most sensitive variables, two more analyses are made, replacing the initial model by a Mohrs constitutive model, which considers the material as continuous. The results obtained from the Ubiquitous-joint model provide an acceptable representation of the field conditions, showing a failure mechanism type of rockfall from the face of the slope in the rhyolite, and the rupture surface of the breccia, without propagation of surface failure. In the analysis, when considering both materials as continuous, it is not possible to take account the fault conditions simultaneously, and this analysis also requires values of the mechanical parameters different from those recommended in literature.

Pilar-barreira entre painéis de lavra para a mina de carvão

The function of the barrier pillar is to protect the mining panel in activity from the abutment load of adjacent mining panels that were mined. In the case of underground mines in Santa Catarina State, the barrier pillar has functioned to protect the main entries of the mine against pillar failure from old mining panels. The objective of this paper is to verify the application of the empirical method to design barrier pillars as proposed by Peng (1986), using numerical simulation following the mining geometry of the coal mines in Santa Catarina State. Two-dimensional numerical models were built taking into account the geometry of the main entries and mining panels for different overburden thickness, and considering the geomechanical properties for the rock mass that forms the roof-pillar-floor system for the Bonito coal vein. The results of the simulations showed that the empirical method to determine the barrier pillar width is valid for the studied coal vein and considered mine geometry. Neither did the pillar at the main entry become overstressed due to adjacent mine panels, nor did the roof present any failure due to stress redistribution.

Classificação geomecânica em projetos de reforço do teto em mineração de carvão

The pillar and roof support design should take into account the rock mass mechanical behavior and excavation method (blasting or mechanical excavation). This work aims to improve the approach for roof support design in underground coal mines to reduce the risks of roof failure and determine the adequate roof support for each kind of roof typologies found in the mine area. This design approach is based on geological mapping and geomechanical classification CMRR - Coal Mine Roof Rating. This engineering tool describes qualitatively the geological and geomechanical conditions of the roof rock mass for coal mines to select appropriate roof support. Different classes of CMRR were identified at Barro Branco coal mine. Therefore, based on the CMRR classification it was considered the maximum roof span at crossings, bolt length and bolt load capacity. The methodology is adequate to reduce roof falls and predicting the adequate support for different roof typologies for different zones in the mining.