Ventilation Design Modeling and Optimization for an Underground Bauxite Mine

Underground bauxite mining exploitation is a challenging environment for ventilation. In this paper, such a complex underground ventilation network is modeled in detail using the Ventsim software. The network and its characteristics are selected and developed through the software, followed by their calibration and validation against actual measurements of both airflow quantity and quality which have been carried out at the mine site. This model constitutes the base of the new ventilation design for the future mine expansion. The recommendations and the characteristics for the optimization of the new proposed design are finally presented in detail.

Soil-Water Separation Property of Bauxite Mine Slime

Traditional disposal of the high-water content slime from the beneficiating and washing of the bauxite mine requires lots of land and a long time to consolidate, which has attracted a wide range of environmental and social concerns. High-speed centrifugal test was carried out to investigate the water property and composition of high-water content bauxite washing mud. Test results indicated that the bound water content ranged from 29.7% to 31.4%, free water content ranged from 250.6% to 252.3%. The bound water accounted for only 11%, while the free water accounted for about 89% of total water content. A series of model tests were conducted to study the slurry-water separation property of high-water content bauxite mine slime. Experiments showed that controlling the vacuum load application process can effectively inhibit the formation of low-permeability stratum around the drainage body. The final settlement increased by 31.5% and the amount of water discharge increased by 39.52% compared with the conventional vacuum preloading method. Moreover, the water content may decrease from 281.9% to 53.6% within 60 hours with the increase of density of drainage body under the controlled vacuum load application process.

Assessment of Naturally Occurring Radioactive Materials (NORM) in Mining Residues and Environmental Material from Sefwi, Awaso Bauxite Mine

Gamma ray spectrometry was used to quantify level of NORM in mining residues sampled at Awaso bauxite mine and surrounding communities. The radionuclides of interest were 238U, 232Th and 40K and the radioactivity levels were determined in soil, bauxite ore, red mud and water samples from wells. The radioactivity concentrations in soil, bauxite ore and red mud 238U, 232Th and 40K were 18.01±1.96 Bqkg-1, 19.07±2.12 Bqkg-1 and 103.21±1.74 Bqkg-1; 39.42±4.18 Bqkg-1, 97.32±10.63 Bqkg-1 and 14.68±1.82 Bqkg-1; 44.85±4.79, 64.23±6.58 and 125.30±18.72 Bqkg-1. The activity levels for both 232U and 232Th were above world-wide average values while Potassium-40 levels were lower. The mean activity concentration values of 238U, 232Th and 40K in water samples were 1.49±0.45 Bql-1, 3.68±0.69 Bql-1 and 15.69±0.28 Bql-1 respectively and were within the world average activity concentrations except for bauxite ore and red mud. The committed effective dose was 0.74 mSv and annual effective dose estimated to be 0.136 mSv which is below recommended dose limit of 1 mSvyear-1 for public exposure.

ENVIRONMENTAL IMPACTS ASSESSMENT OF TASH BAUXITE MINE IN SEMNAN PROVINCE, NORTHERN IRAN

Mineral resources and mining are the pillars of development in any country. Mining development must be performed based on the pillars of sustainable development to prevent the damage to water, soil, air, plants, wildlife and social life of local communities by exploiting valuable minerals and economic development. Lack of attention towards the pillars of sustainable development in the long-term can turn into serious damages to environment and social life of local communities. There would probably be needed to spend multiple times more than the added value earned by the mineral production in order to recompense the environmental and social damages caused by unauthorized mining. Therefore, from the late 2001 the beginning of mining activities in the Bauxite mine of the village of Tash has caused challenges for the environment, natural resources and social issues. Some of the most important of which are loss of water reserves in the region, the pollution of ground and surface waters, soil erosion, susceptibility of the region to dust, loss of vegetation and rangelands, the endangerment of wildlife, flooding due to inappropriate tailings depot. This paper addresses to the causes of these pollutions and how to stop further damages of the process.