Open pit mining method

Open pit mines are gradually formed during infrastructure and production. The task is to build infrastructure during the build power and water supply systems and transportation lines, construction of mineral processing plants, waste dump and machinery repair and other major structures and facilities, as well as the completion of registration and the amount of mining engineering when production stripping necessary. In the production process, in order to complete the annual ore production tasks specified in the production plan, it is necessary to complete certain development, precision and stripping engineering quantities on time. In the mining process of open pit mines, the ore and rock in the boundary must be divided into horizontal stratification of a certain thickness so as to be mined from top to bottom. These stepped working faces are called steps. Most of the steps use separate perforation and mining equipment.

The steps are mainly composed of the following elements:

Upper flat plate 1 - the upper horizontal plane of the step;

Lower flat plate 2 - the lower level of the step;

Step slope 3 - a step slope facing the goaf;

Slope angle a - the angle between the step slope and the lower horizontal plane;

Slope top line 4 - the intersection of the step slope surface and the upper water level;

The intersection line of the bottom slope line 5 and the lower flat plate;

Step height h - the vertical distance between the upper flat plate and the lower flat plate.

Open pit metal step height is generally 10-value = "14" unitname = "m"> 14m.

The production of open pit mines is carried out according to the determined production process, which is collectively referred to as mine engineering. Mine engineering can be divided into stripping and mining projects. The stripping project is to remove the rock that affects the mining in the open mine boundary and transport it out of the open mine boundary to ensure the normal operation of the mining work. The newly-opened open pit mine stripping and mining projects are carried out in sequence, and in normal production, they are carried out simultaneously. This is the policy of “extraction and stripping, stripping first” prescribed by China's mining industry. If this policy is not implemented seriously, it will not be able to ensure that the mine is in normal condition and will continue to complete the ore production task. According to the role of mining engineering, it can also be divided into development, mining and expansion projects. The pioneering project is to dig the inclined access ditches according to the development system specified in the design to establish the transportation connection between the ground and the production level of the mining site; then to dig into the horizontal section trenches to establish the initial working line of the step mining. The expansion project is carried out on one side (or both sides) of the opened trench. In the future, the mining procedures at the same level are the same as the first level, that is, first digging into the ditch, then opening the sub-level ditch, and then carrying out the expansion project. In short, open-pit mines are mostly developed from a single level to a multi-level, gradually forming a development system for the whole mine. . Open Pit layer by layer from the surface down to start mining, the use of rail transport, transport route but also by the shallow and deep, with the development of mining projects progressively rolling, when the end of open pit mining, transport route was finally formed.

In the mining site, the slope of the rock below the ore body is called the bottom gang. The slope of the rock on the upper part of the ore body is called the top gang. The slope at the two ends of the mining site is called the end gang;

The final slope line BE and CF ------ the line connecting the top line of the last non-working step and the bottom line of the last non-working step;

The final slope angles ß and δ---the angle between the final slope line and the horizontal line.

In order to ensure that the open pit mine has normal working conditions, the width of each mining level working plate should be not less than the minimum flat disk width. Its size is determined by the width of the pile, the specifications of the transport equipment and the conditions of passage. Figure nth="8" year="2005"> 5-8-5 is the minimum working plate width component.

B _minimum = Bvalue = "10" unitname = "C"> ten C ten T ten Z (m)

Where: B _minimum - minimum working plate width ( m);

B—burst width ( m).

- The width of the explosion stack varies with the height h of the step and the hardness of the rock. If the piercing punch is used for perforation, the range of the step width when the single row of holes is blasted is shown in the table nth="8" year="2005">5-8- 1.

Table nth="8" year="2005"> 5-8-1 explosion width

C. The distance from the bottom line of the pile to the edge of the transport equipment ( m).

T—width required for vehicle operation ( m);

Z1 is a safe distance ( m) for preventing rock mass sliding .

The minimum working plate width can be selected according to the data listed in the table nth="8" year="2005"> 5-8-2. When transporting by rail, the minimum flat disk width can be taken as the upper limit, and the lower limit can be taken when transporting the car. For example, when using double track (line) transportation, the distance between the center lines of the line should be added.

Table nth="8" year="2005"> 5-8-2 minimum working plate width

China is a country with vast resources and abundant mineral resources. There are various types of ore bodies buried underground. What conditions should be available for open-pit mining?

Since open-pit mining is taking out ore, a certain amount of rock must be stripped. Moreover, the amount of stripped rock directly affects the cost of mining ore and the amount of unit investment, and the number of stripped rocks often varies as the depth of mining changes. Therefore, the essence of determining the reasonable open-pit mining scope is to determine the reasonable open pit mining problem, and secondly, to determine the mining range of the open-pit mining site on the surface.

In order to determine the depth of reasonable open pit mining, we must first understand the concept of stripping ratio. Because the amount of exfoliated rock in the open pit directly affects the ore cost and unit investment, the amount of rock to be stripped from the unit ore must be calculated. This ratio is called the stripping ratio. Its unit can be expressed in tons per ton or m ³ . There are many forms of stripping ratio, and the following are commonly used to determine the open-pit mine boundary:

1) Average stripping ratio (n _level ): the ratio of total rock mass to ore volume within the open mine boundary.

n _flat = (B ₁ + B ₂ ) A m ³ / m ³ (t/t)

Where: B ₁ , B ₂ —— the total amount of rock in the open-pit mine boundary, m ³ (t);

A - the total amount of ore in the realm, t or m ³ .

2) stripping ratio state (n _territory): i.e., open pit increases to a certain depth (typically a step height), the ratio of the rock must be taken out of the amount of ore.

n _境 =( b1+b2)/a m ³ /m ³ (t/t)

Where: b ₁ , b ₂ —— the amount of rock that must be produced in the open pit to increase a certain depth, m ³ (t);

a - increase the amount of ore produced at a certain depth, t or m ³ .

3) economical stripping ratio (n _via): i.e., using the maximum allowable open-pit mining stripping ratio economically. There are two ways to determine it:

1 Determined based on the comparison of open and underground mining costs:

_by n = (ca) / bt / t

Where: c----- mining by underground mining method - the cost of ore, yuan / t;

a-----exploiting the cost of one ton of ore in open pit, yuan / t;

b-----Explode the cost of one ton of rock, yuan / t.

The above data can be selected according to mines with similar conditions.

2 According to the sale price of ore, the ore sales price is determined by the market.

_by n = (c ₀ -a) / b

Where: c. -----The price of this kind of ore (yuan/t). a and b are the same as the above formula.

Under normal circumstances, the economic reasonable stripping ratio should not exceed the value specified in Table nth="8" year="2005"> 5-8-3.

Table nth="8" year="2005"> 5-8-3 economically reasonable stripping ratio ( m ³ /m ³ )

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