Paulo Salvadoretti

Estimativa de qualidade de carvão por meio de perfilagem geofísica de gama natural e resistividade

This study investigates geophysical logging as a tool to predict coal quality. Some of the coals chemical parameters were determined by laboratory analysis and were compared against values derived from geophysical logging correlation (natural gamma radiation and resistivity versus ash content, specifically). The results showed a strong correlation between the coals natural gamma emissions and their ash content. From this correlation, a simple linear model was obtained and used to estimate ash grades, directly from geophysical logging records. The error of these predictions is less than ± 5%. Additionally, results showed no correlation between the sulphur grade, or volatile matter, and the geophysical records. Ash grades derived from natural gamma ray values can be usedas secondary information to evaluate coal quality during resource estimation, when combined with lab analysis and appropriate geostatiscal methods. The methodology is illustrated by means of a case study at a coal deposit located in southern Brazil.

Estimativa de parâmetros indicadores de qualidade de carvão a partir de perfilagem geofísica

Coal quality is commonly analyzed using cores obtained from diamond drill holes, which are costly and time consuming. Geophysical logging provides an indirect measurement of coal quality derived from some physical properties logged by the probe. Among the geophysical logging methods, gamma back scattering (gamma-gamma) is appropriate for identifying coal seams and for inferring some coal quality parameters. This study identifies the possible correlation between gamma-gamma readings and ash content. By using the logged geophysical survey values plotted against the ash content, analyzed at the same intervals, a scatter plot was constructed and a model adjusted. The derived model showed a high correlation coefficient and acceptable estimation error, recommending this practice for obtaining quick, low-cost information for mine planning.

Benefício do adensamento amostral com perfilagem geofísica no planejamento de lavra a curto prazo

Core samples obtained by drilling surveys are a current practice in the mining industry and are extremely important to mineral exploration and mine planning. However, this type of information is expensive to be obtained and is frequently used for short term mine planning. Diamond drill holes are commonly sampled at a large sampling spacing incompatible with the resolution required for short term mine planning. This study compares the volume estimated using data from borehole cores drilled in a grid of 140 x 140 m with the volume calculated from data obtained by geophysical logging in a grid of 10 x 10 meters. The study analysed the volume of a block delimited by few blast holes. There was a very significant difference between the volume calculated from borehole core samples and the actual volume. However, there was no significant difference between the actual volume and the volume calculated from data obtained by geophysical logging. Thus, it can be concluded that a widely-spaced sampling mesh is not enough to foresee short term production for the case study. However, geophysical logging can be used for this purpose without disturbing mining operations; it also gives immediate results, with easy and fast data acquisition at substantially low costs.

Construção de um modelo computacional para o circuito de ventilação da Mina Esperança

Mine ventilation aims at providing fresh air for all working faces at an adequate flow to assure an appropriate atmosphere to the miners. The design and efficiency analysis in a ventilation circuit can be carried out using Hardy Cross algorithm and Kirchhoff law. In a complex ventilation layout these techniques proved to be extreme laborious. For a more detailed analysis or checking the effect in the ventilation circuit due to mining changes, computational simulation can be used. These simulation methods were used to construct models for Esperanca Mine (Brazil). The model construct by simulation aim at checking the adequacy of the ventilation circuit to the NR22 (Brazilian regulation). Also a scenario providing 2000 m3/min for each panel was studied. Information necessary to the model include: static pressure, openings dimensions and geometry, and fans operational characteristics. The output from the model includes air flow and pressure along the circuit. Differences between the values predicted by the model and true values are less than 20%. The model was accepted as valid and therefore used for simulating the ventilation at various mining layouts. Computational ventilation models demonstrate their usefulness in planning and improving underground atmosphere.

Monitoramento geofísico de desmonte de rocha com utilização de explosivos em condições de risco elevado em zona urbana

This paper presents an application of geophysical methods to evaluate the risk associated with blasting used during rock excavation at highly populated and risky urban areas. Ground penetration radar provided information related to rock mechanics such as fracture density, whilst seismographic readings helped in maintaining vibration levels below maximum limits. Results of in situ soil and rock characterization and vibration control are reported and discussed. The methodology proposed is illustrated in case study.