تحلیل ریسک

The first step for carrying out mining operations in surface mines is to build a network of communication routes to access different parts of the mine, and also transport ore and waste. For the successful design of ramps in open pit mines, it is necessary to evaluate and analyze the related safety risk based on the geological conditions, geomechanical characteristics, type of machinery, and the mine design. In this research, the ramp safety risk was investigated to determine the accident-prone zones.  In this regard, the information obtained from the exploration boreholes of the Chadormalu iron ore mine was used for modeling. At first, the economic block model of the mine and the ramp were modeled in different scenarios. After selecting the optimal ramp, the total length of the ramp was zoned at 100-meter distances to assess the safety risk in 42 zones, and to identify accident-prone zones by calculating the total risk index. Thus, by drawing a bow-tie diagram, the five initial events including wall instability, car crash, stone throwing, slippery, and accident were identified as the main events leading to incidents; then the probability and consequences severity of each initial event were determined. According to the results, the car crash and wall instability events have the most negative impact on the ramp safety. Also, the highest and the lowest values of the total risk index were 110 (in zones 37 and 42) and 5 (in zones 4, 5, and 9), respectively.

Bentonite is an industrial soil with thousands of applications. Most of the Iranian bentonite mines, especially the mines of South Khorasan province, which is the center of the Iranian bentonite, are operating in a semi-closed or limited operation due to lack of reserves and dispersion. The construction of mobile processing plants will boost these mines, create added value, create jobs in deprived areas and make proper use of the country's reserves. In addition, flexibility, reducing the cost of transporting raw materials, the need for low investment, quick and easy installation and improving the knowledge of equipment manufacturing and mining are also the most important advantages of these processing plants. A mobile processing plant to produce bentonite concentrate requires primary crushing (jaw crusher), secondary crushing (impact crusher), heavy intermediate separator (cyclone or Dyna whirlpool), drying (rotary dryer), grinding (roller mill), packaging, power supply and control and monitoring units, that each of them can be mounted on a trailer. Technical and economic studies show that such a mobile processing plant with a capacity of 200 tons per day requires about 530 billion rials of fixed capital and about 30.5 billion rials of working capital. Also, the annual operating costs of this project are estimated at about 180 billion rials. With these specifications, the plan will have a payback period of 1.8 years, a positive net present value and an internal rate of return of 48%, which is appropriate and cost-effective in terms of investment. Also, the most important risks of this plan in terms of investment include operating processes, exchange rate fluctuations and prices. Other parameters of this plan are medium and low risk>

Dimensional stone mining includes tedious activities. It is necessary to study the safety and risk analysis with respect to the large volume of the diamond wire saws used and the number of accidents occurs in quarries. In this study, a safety risk analysis is done for Badeki marble quarries using FMEA method identifying the accidents happened in the mines. The results of analysis and ranking the risk of accidents showed that, wire saw tearing and rock fall are the biggest thread in these quarries. The average safety risk before and after reducer action in the quarries studied are 17.33% and 5.33%, respectively. It indicates a 69.23% decreasing trend in the total risk in these quarries. The results of this study showed that the initial risk in these mines can be greatly reduced by doing some changes and some preventive notices to secure the equipment and personnel.

Ore reserve amount and grade are critical variables in determining technical and economical indicators. These factors always associate with uncertainty. Therefore it is essential to assess risk along with them by using appropriate methods. One of these methods is conditional simulation that allows providing probability maps and determining orebody risk rate. Unlike the common geostatistical estimation methods which involve some sort of smoothing، conditional simulation provides a tool for quantifying risk rate along with grade and design and planning parameters. In this research sequential Gaussian simulation has been applied to assess the uncertainty associated with reserve grade and tonnage of Esfordi phosphate mine and prepared confidence interval and E-type maps. Finally، the rate and the effect of estimated risk have been assessed and analyzed. According to simulation result، ore reserve of Esfordi mine is between 12/212 and 18/835 tones and the average of ore amount is 15/269 with average grade of 16/8%. The results show 30% -risk with blocks.

In underground coal mines, due to occurrence of probable events and the consequent risks, normally a reliable safe environment is not provided for the work forces and operational equipments. Through the risks, two main considerable damages may happen. First, the human injuries namely fatality, disability or maim and organ fractures and second the economical damages such as amortization and loss of mining equipments, and closure of working faces and galleries. Considering these types of crucial events this study aims on reducing the likely risks particularly in East Alborz Coal Mines Company. For this purpose, based on probability of event occurrences, their severities and outcomes the relevant risks have been assessed and analyzed. To achieve this goal by taking into account the occurrence probability and intensity a number of measures or standards were developed by the authors. Risk Priority Number (RPN) was introduced. By employing RPN the most impressive uncertainty factor in East Alborz Coal Mines Company was recognized. Finally, with the regard to the degree of damages caused by the events, a practical procedure for risk reduction in the mines has been presented.

In any mining project, specially when the ore reserve is relatively large and distributed inhomogeneously, drilling new boreholes to reduce the uncertainty associated with the grade estimation as well as reserve classification becomes unavoidable. However, selecting the optimum location of the new borehole, in terms of providing the maximum amount of information possible is a challenge. In this regard, customarily, the geostatistical approaches, based on minimizing the estimation error (variance) of blocks grade is used. However, in this method, the estimation variance of each block is independent of the sample grade values and only takes into account the spatial distribution of sample’s location. This will ignore the local variability of sample values. Another approach to determine the optimum location for the new drilling boreholes could be based on the geostatistical simulation techniques. In simulation methods, the spatial variability due to the sample location, as well as the local variability associated with the data values are taken into consideration. In this paper, the Fractal Conditional Simulation Method (FCSM) is used to simulate the iron grades of anomaly No.3 of Gol-E-Gohar iron ore mine. The simulated data, then, were used to estimate the iron ore reserve and to perform a risk analysis. This method simulates the data sets, while the fractal co-dimension as well as the statistical and geostatistical parameters are kept unchanged. Finally, using uncertainty index and GET (Grade, Error and Thickness) function, the optimum location for new boreholes in the northern part of the ore-body was suggested.