Javier Taboada Castro

Method for the Evaluation of the Reserve of a Metallurgical Quartz Deposit by Advanced Kriging Techniques

There are several different methodologies for the evaluation of the reserve of a mineral deposit. Traditionally, classic methods of volume computation for mineral deposits have been used to evaluate the reserve according to its commercial quality. Nevertheless, in previous works it has been demonstrated the functionality of the advanced kriging techniques applied to granite batholiths. Comparing fuzzy kriging techniques with universal classical kriging, it was concluded that the fuzzy techniques had good results for planning the selective mining of the ornamental rock deposit. Since geostatistical methods had good results, these techniques are applied to a metallurgical quartz deposit in this work. The objective of the investigation is to develop the most adequate technique for the determination of the different material qualities in this type of deposits, where the chemical composition of the mineral (aluminium oxide and impurity contents) mainly determines the grade. The obtained results show that the compositional kriging technique is more adequate than fuzzy methods for this type of deposits, allowing a sufficiently coherent prediction of the distribution of grades in the deposit. Based on the results, a 3D geostatistical model composed of cubed cells was done as well. The model provides a visual tool, easy to put into practice for the exploitation management. Keeping all this in mind, the selective mining of the reserves would be possible, being that fact necessary to compete in the rising, competitive world market.

Tests for the Optimization of Cut-Off Parameters for Seven Galician Granite Varieties

The ornamental rock sector in Galicia (NW Spain), in particular the granite extraction and processing sector, has undergone tremendous development in recent years as a direct consequence of the use of non-aggressive rock mass extraction methods and the progressive modernization and automation of the different processes for processing and finishing the slabs, as well as the improvement of in-plant logistics. Nevertheless, it has been ascertained that cutting parameters entered as setpoint values in the diamond circular saws, used for the subdivision of slabs of the different commercial granite varieties, do not fit clear technical criteria for the optimization of cutting efficiency, but are selected and pre-set based on the experience of the circular saw operator. In order to evaluate the validity of thus selected cutting parameters and to provide the sector with a more objective tool, the cutting performance of seven granite varieties from Galicia which have high sales was analysed. Thus, each available slab was subdivided using four different cutting settings resulting from modifying two of the parameters which most affect cutting efficiency: cutting speed (m/min) and cutting depth (mm). These parameters, in turn, have an influence on power consumption (kWh), diamond saw blade wear (mm) and average production (mm2/min). Thereby, an exhaustive data acquisition process was carried out in order to create a complete database with the representative information of the cutting of each of the seven tested varieties and determine the optimum configuration for cutting each material, based on the results of a graphical analysis of the mean of data and the analysis of the variance (ANOVA).

Study on Occupational Safety in the Aggregates Sector

The aggregates sector is a key national and international mining sector in terms of both production and value. The rate of workplace accidents (number of accidents during working hours per 100,000 workers) for the mining sector in Spain is considerable, with the rate for Galicia below the national rate until 2007 and slightly above the national rate from 2007 to 2010. We analysed occupational risk prevention in the aggregates sector in Galicia in the three years 2005 to 2007, based on the information provided by 65 companies. This survey period was before the international crisis so the data provide an overview of the sector at its peak, when the consumption of construction aggregates was high. For the same reason the workplace accident rate was considerably higher than the current rate (corresponding to a period of low activity), so the described scenario can be considered as the most adverse situation in terms of occupational risks. The specific objectives of the study were to evaluate general occupational risk prevention management systems in companies in the mining sector and to study compliance with occupational noise exposure and dust control regulations. The information was gathered in the companies via a questionnaire administered in personal interviews. The occupational risk prevention management systems of aggregates companies in Galicia were evaluated and strengths, weaknesses, opportunities and threats facing the sector were identified.