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1 The final slope element shall be determined in accordance with the following provisions:
(1) The height of the step shall be determined in accordance with the provisions of Table 1 below;
Table 1 Â Step height
Note: When the excavator or loader is installed, the height of the explosion should not exceed 1.5 times the maximum excavation height of the machine .
(2) The slope angle of the step should be selected according to the provisions of Table 2 ;
Table 2 step slope angle
Note: The values ​​in the table can be adjusted according to the development conditions such as joints, fissures and bedding, and the direction of the reverse slope or the direction of the slope.
(3) The width of the safety platform should not be less than 3m ; when the final steps are in parallel, there is no safety platform;
(4) A cleaning platform should be provided every 2 to 3 safety platforms. When cleaning manually, the width of the cleaning platform should not be less than 6m ;
When cleaning mechanically, the width of the cleaning platform shall be determined according to the requirements of the equipment, but shall not be less than 8m ;
(5) When the final slope of the open pit mine adopts multiple steps and the number of sections is not more than three .
2 The method for determining the economically reasonable stripping ratio should meet the following requirements:
(1) The economic rational stripping ratio should be calculated by the profit comparison method;
(2) When the value of ore is not high and the underground mining is profitable, it can be calculated by the cost comparison method;
(3) For deposits that are only suitable for open pit mining, the economic stripping ratio can be calculated by the price method.
3 The demarcation of the open-pit mining boundary shall comply with the following provisions:
(1) The ratio of stripping and mining in the realm should not be greater than the ratio of economically reasonable stripping;
(2) deposits of precious metals and rare metals, can be no greater than average stripping stripping ratio delineation economical;
(3) Irregular deposits with large changes in thickness and complex topography should be delineated by the ratio of stripping ratio of the boundary to no more than economically reasonable stripping ratio, and the average stripping ratio should be no more than the economic reasonable stripping ratio for checking;
(4) When the stripping ratio of the realm is not greater than the economic rational stripping ratio and the open-pit mining boundary is defined, when the reserves outside the border are small and it is difficult to recover by underground mining, the economic stripping calculated by the boundary stripping ratio not greater than the price method should be adopted. Than, it is advisable to expand the open-pit mining realm;
(5) Deposits with large thickness of ore layer and small stripping ratio can be delineated according to the degree of control of the deposit and the service years;
(6) The length and width of the bottom plane of open-pit mining should meet the requirements of shovel equipment and transportation equipment;
(7) The comprehensive technical and economic comparison of open-pit and underground mining methods should be carried out for deposits with a large amount of infrastructure and the initial production and stripping ratio.
(1) The height of the step shall be determined in accordance with the provisions of Table 1 below;
Table 1 Â Step height
| Mineral rock properties | Mining operation | Step height m | |
| Soft rock | Mechanical shovel | Not blasting | Not more than the maximum digging height of the machine |
| Hard and stable ore | blasting | Not more than 1.5 times the maximum digging height of the machine | |
| Sandy ore | Artificial mining | Not more than 1.8 | |
| Soft ore | Not more than 3.0 | ||
| Hard and stable ore | Not more than 6.0 |
(2) The slope angle of the step should be selected according to the provisions of Table 2 ;
Table 2 step slope angle
| Platts coefficient f | 14 to 8 | 7 to 3 | 2 to 1 |
| Step slope angle ( ° ) | 75 to 70 | 65 to 60 | 60 to 45 |
(3) The width of the safety platform should not be less than 3m ; when the final steps are in parallel, there is no safety platform;
(4) A cleaning platform should be provided every 2 to 3 safety platforms. When cleaning manually, the width of the cleaning platform should not be less than 6m ;
When cleaning mechanically, the width of the cleaning platform shall be determined according to the requirements of the equipment, but shall not be less than 8m ;
(5) When the final slope of the open pit mine adopts multiple steps and the number of sections is not more than three .
2 The method for determining the economically reasonable stripping ratio should meet the following requirements:
(1) The economic rational stripping ratio should be calculated by the profit comparison method;
(2) When the value of ore is not high and the underground mining is profitable, it can be calculated by the cost comparison method;
(3) For deposits that are only suitable for open pit mining, the economic stripping ratio can be calculated by the price method.
3 The demarcation of the open-pit mining boundary shall comply with the following provisions:
(1) The ratio of stripping and mining in the realm should not be greater than the ratio of economically reasonable stripping;
(2) deposits of precious metals and rare metals, can be no greater than average stripping stripping ratio delineation economical;
(3) Irregular deposits with large changes in thickness and complex topography should be delineated by the ratio of stripping ratio of the boundary to no more than economically reasonable stripping ratio, and the average stripping ratio should be no more than the economic reasonable stripping ratio for checking;
(4) When the stripping ratio of the realm is not greater than the economic rational stripping ratio and the open-pit mining boundary is defined, when the reserves outside the border are small and it is difficult to recover by underground mining, the economic stripping calculated by the boundary stripping ratio not greater than the price method should be adopted. Than, it is advisable to expand the open-pit mining realm;
(5) Deposits with large thickness of ore layer and small stripping ratio can be delineated according to the degree of control of the deposit and the service years;
(6) The length and width of the bottom plane of open-pit mining should meet the requirements of shovel equipment and transportation equipment;
(7) The comprehensive technical and economic comparison of open-pit and underground mining methods should be carried out for deposits with a large amount of infrastructure and the initial production and stripping ratio.
Introduction:
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Features:
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