The optimal method of rock excavation was revealed. The hangar area was determined for the development of mines with dredges of different standard size. The application of the proposed method for straight and oblique dredging was considered. The authors have calculated hangar sizes while all sizes were accepted minimum for reducing the cost of construction and keeping the heat inside it. It is revealed that the application of the proposed method will extend the dredging season, or even make it year-round. The developed mathematical model allows determining the temperature inside the isolated space of the open-pit dredging depending on the water temperature of the open-pit and the ambient air temperature.
This allowed obtaining the distribution of thermal fields in the constructed experimental hangar. Thermal sensors and an infrared camera were used to record the results. The hangar model was performed on a scale in compliance with geometric similarity. An experiment was conducted to confirm the effectiveness of this method by creating a facility in the form of a hangar model. It was revealed that the most perspective material to isolate dredges was polycarbonate, possessing a number of advantages. Existing structures are used to store mineral dumps, protect the environment from dust, as well as for other purposes. The authors propose a method to isolate the open-pit mine with artificial materials, as well as consider the application of similar structures in the dredging industry. The article presents the review of the existing methods aimed at extending the dredging season, providing their systematization, which is based on the methods of water lanes' maintenance and formation in the open-pit dredging. In consequence, dredging operations are terminated until the occurrence of favorable conditions for work. During the period of subzero air temperatures dredge performance decreases significantly due to the icing of dredge structure. This problem is particularly relevant for deposits located in the Far North, where the dredging season is limited by climatic conditions. The article deals with the problem of reducing dredge performance when operating at subzero air temperatures. The study draws attention to small changes in design that allow bucket line dredges of medium to large size to become BAT sufficient to satisfy stringent environmental concerns. The goal of the study was to identify 'Best Available Techniques’ BAT for bucket-line gold dredges. The study assesses the advantages and disadvantages of large, medium and small bucket-line dredges in terms of mining and impacts. Just as important has been the success of local manufacturers in cutting costs, adopting new ideas such as Caterpillar chains for the bucket, and the ease of making small bucket-line dredges in simple workshops. The persistence of bucket-line gold dredges in Siberia and Asia is not only due to the presence of large gold placers suitable for dredging. The decline of bucket-line gold dredges in North America and Australasia is due to exhaustion of the richest placers suitable for dredging, increased concerns about the environment, and the very high capital cost of large capacity machines.
Rather than being out-dated technology the remain at the cutting edge in terms of efficiency, effectiveness, reliability and profitability. The study shows bucket-line gold dredges are still being manufactured and launched in Siberia, Mongolia and China. Yet such dredges are still active in large parts of the world. None of the authorities are doing anything to stop illegal mining, which has become a epidemic in the Amazon," Aguiar of Greenpeace Brazil said.Bucket-line gold dredges have existed for more than a century and in North America and Australia and are preserved as relics. The Federal police said it was looking at the best way to deal with the problem and prevent environmental damage.
The ANM said it did not fall under their purview as they only oversaw legal mining, while criminal activity was a matter for the police and courts. River traffic and pollution was the Navy's area, IPAAM said. The IPAAM said in a statement that the rafts anchored on the river were under federal jurisdiction, so the National Mining Agency (ANM) was responsible for licensing and it was up to the federal police to see if any crimes had been committed. The dredging rafts have floated downriver from the Humaita area, where there has been a surge in illegal gold mining, and were last seen some 400 miles (650 km) away in Autazes, a municipal district southeast of Manaus.Ī spokesperson for Brazil's environmental protection agency Ibama said the illegal dredging on the Madeira river was the responsibility not of the federal government but of Amazonas state and its environmental agency IPAAM.
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