Effects of Blast Vibration on Unplanned Dilution in an Underground Metal Mine

نوع مقاله: مقاله پژوهشی

نویسندگان

دانشکده مهندسی معدن، نفت و ژئوفیزیک دانشگاه صنعتی شاهرود

10.29252/anm.8.17.77

چکیده

One of the factors affecting overbreak or slough of the roof and walls of underground stopes, causing unplanned dilution is blast vibration. The amount of damage caused by earth vibration can be measured in terms of peak particle velocity (PPV). In this study, in order to investigate the effects of blast vibration on the occurrence of unplanned dilution, 72 three-component records acquired upon 24 blasts were obtained at underground Venarch Manganese Mines. Once finished with data analysis, scale distance was used to propose an exponential equation for predicting PPV based on the cubic root of the charge weight per delay. Then, the effect of blast vibration on walls and roof of the stope was examined on 24 different explosions, dilution values were recorded at various scaled distances to the face, and the relationship between them was determined. Equivalent linear overbreak/slough (ELOS) was used to determine dilution, with cavity monitoring system (CMS) being used to calculate it. Then a practical diagram was presented to predict the boundary of the dilution area from the explosion. Finally, The relationship between the amount of ELOS against the PPV was presented and it was determined if the PPV was fewer than or equal to 6.73 mm / s, the dilution will not occur.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effects of Blast Vibration on Unplanned Dilution in an Underground Metal Mine

نویسندگان [English]

  • Madjid Mohseni
  • Mohammad Ataei
  • Reza KhalooKakaie
Dept. of Mining, Petroleum and Geophysics, Shahrood University of Technology, Iran
چکیده [English]

One of the factors affecting overbreak or slough of the roof and walls of underground stopes, causing unplanned dilution is blast vibration. The amount of damage caused by earth vibration can be measured in terms of peak particle velocity (PPV). In this study, in order to investigate the effects of blast vibration on the occurrence of unplanned dilution, 72 three-component records acquired upon 24 blasts were obtained at underground Venarch Manganese Mines. Once finished with data analysis, scale distance was used to propose an exponential equation for predicting PPV based on the cubic root of the charge weight per delay. Then, the effect of blast vibration on walls and roof of the stope was examined on 24 different explosions, dilution values were recorded at various scaled distances to the face, and the relationship between them was determined. Equivalent linear overbreak/slough (ELOS) was used to determine dilution, with cavity monitoring system (CMS) being used to calculate it. Then a practical diagram was presented to predict the boundary of the dilution area from the explosion. Finally, The relationship between the amount of ELOS against the PPV was presented and it was determined if the PPV was fewer than or equal to 6.73 mm / s, the dilution will not occur.

کلیدواژه‌ها [English]

  • blast vibration
  • pick particle velocity
  • underground stope
  • unplanned dilution

In mining, the objective is to economically exploit the ore while taking into account safety of work force and machineries. However, generating wastes which contaminate actual ore, so-called dilution, drastically affect direct and indirect costs of mining [1]. Dilution significantly influences the cost of a stope and hence mining profitability as it not only increases costs associated with the stope, but also affects all other cost components incurred by exploitation, transportation, crushing, milling and handling as well as those of the operations to be performed on valueless wastes or low-grade rocks of insignificant value. Moreover, the extra time spent on cutting and filling large stopes developed as a result of wastes ends up with unplanned delays and renewal costs [2].

Dilution reduces revenues of mining projects. Waste exploitation, transportation and processing are costly operations. In fact, each unit of dilution-resulted waste replaces a highly profitable unit of ore in production capacity of the mine. For example, in a gold mine with a processing capacity of 360,000 tons/year, taking average grade of the mineral reserve, gold price, and total operational cost to be 0.35 ounces of gold per ton, 350 USD per ounce and 83.86 USD per ton, respectively, the difference in total revenue between two scenarios with 15% and 20% of dilution level will exceed 4 million dollars per year; further, recovery percentage of the corresponding mineral dressing plant will reduce from 95% to 94.4% as the dilution increases from 15% to 20% [3]. Investigation of the effect of dilution on profitability of a gold vein mine showed that, the mine would lose its profitability at dilution levels exceeding 40%, ending up with some loss [4]. Investigating economic losses incurred by dilution in a thin vein tungsten mine in China, where cut-and-fill stoping method was used to exploit the mine, showed that, 44.4% of the losses incurred by dilution were avoidable [5]. Costs associated with 14% dilution in a gold mine were determined to be about 38 USD per ton. In a year, this sumed up to 5.4 million USD [6].

Various parameters are involved in the development of unplanned dilution in underground stopes. These parameters are divided into three groups of geological parameters (such as ore thickness, stress conditions, quality of walls and roof  of stope, stope depth, discontinuities and their position relative to walls), design and engineering parameters (such as stope geometry, blast parameters and under cutting) and operational parameters (such as tonnage of planned production, extraction rate and production sequence) [7].

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