Manual method for determining the realm of mining

At present, in China's open-pit mining design, the principle of n _j ≤n _{jh is} widely used to determine the realm. The steps and practices for determining the open-pit mining boundary are now described below.

a), determine the minimum base width of open pit mine

The minimum bottom width of the open pit mine should meet the requirements of the transportation and transportation equipment to ensure the normal development of the mine project.

When using rail transport, the minimum base width is open pit

Bmin=2Rwh+T+3e-h _L cotα

Where Bmin one open pit mine minimum base width, m;

Rwh——the radius of gyration of the excavator body, m;

T-one railway line width, m;

h _L one excavator body chassis height, m;

The safety distance between the body of the excavator, the side drapes and the vehicle, e=1.0~1.5m;

The slope angle of the next step of the alpha-one open pit mine, (°).

When transported by car, the bottom width should meet the requirements of car shunting. When using a return-type shunt, the bottom width is

Bmin=2(Rcmin+0.5b _c +e)

If a foldback shunt is used, then

Bmin=Rcmin ten 0.5b _c ten 2e+0.5l _e

Where Rmin - the minimum turning radius of the car, m;

b _c - car width, m;

E——the safe distance of the car from the slope, m;

l _c -- car length, m.

When determining the open-pit mining boundary, if the ore body thickness is less than the minimum bottom width, the bottom plane is drawn according to the minimum bottom width; if the ore body thickness is not much larger than the minimum bottom width, the bottom plane may be bounded by the ore body thickness; if the ore body thickness is large At the minimum base width, usually plotted as the minimum base width, and determine the position of the open pit bottom by the following factors:

(1) Maximizing the amount of mined material in the boundary and minimizing the amount of rock fragmentation;

(2) Make the most profitable mining volume, usually the open-pit mine bottom should be placed in the middle of the ore body to avoid the impact caused by geological mapping errors;

(3) According to the ore grade distribution, the quality of the ore produced is the highest;

(4) Adjust the position of the open pit bottom according to the physical and mechanical properties of the rock, so that the slope is stable and easy to wear.

b) Select the final slope angle of the open pit mine

The final slope angle of the open pit mine has a great influence on the stripping ratio.

As the mining depth increases and the slope angle decreases, the amount of rock removal required will increase sharply. Therefore, from the perspective of economic effects, it is desirable to have the slope angle as large as possible; however, many mines are blindly pursuing steep slopes. It caused landslide accidents and seriously affected production. Therefore, safety factors and economic factors should be considered at the same time. Under the premise of ensuring the safety of open pit mines, the final slope angle should be as large as possible to reduce the amount of peeling.

Because slope stability is affected by a series of factors such as physical and mechanical properties of rock mass, geological structure, hydrogeology, slope failure mechanism, and blasting vibration effects, although there are many mathematical calculation methods (such as two-dimensional and three-dimensional limit equilibrium calculation methods, Initial slope optimization design methods such as finite element analysis, probabilistic statistical analysis, and scientific data are provided by means of mathematical models and computer programs, but they are not perfect in practical applications. Therefore, when the mine design selects the slope angle, the analogy method is adopted, that is, the actual data of similar mines are selected. Mines with complex engineering geological conditions are determined by calculation methods after the engineering department conducts engineering geological surveys.

The so-called analogy method, that is, the design department according to the engineering practice, according to the geological conditions, hydrogeological conditions, slope height and shape, age, etc. of the rock mass that constitutes the slope, a large number of statistical data and experience tables combined with the designer The experience of selecting the slope angle. Slope angle listed in Table 8-1, for the metallurgical sector experience in mine design reference value when the slope angle of the primaries by analogy.

The slope angle selected by the analogy method in the design should meet the requirements of mine production technology. In order to ensure the normal production of the mine, the open pit slope usually consists of a safety platform, a cleaning platform, a transport platform and corresponding slopes, as shown in Figure 8-2-9.

Figure 8-2-9 Slope composition of open pit mine

The safety platform a is generally not less than 4m. The cleaning platform b is generally set every 2 to 3 steps, and the width thereof is to ensure the normal operation of the cleaning and transportation equipment. When the transport platform coincides with the safety platform or the cleaning platform, the width is increased by 1 to 2 m. In recent years, in view of the fact that safety platforms and cleaning platforms often fail to function due to insufficient width, many mines have eliminated the safety platform and merged the two steps together, and then set up a cleaning platform with a width of 8 to 12 m. It has also been proposed to combine 4 to 6 steps and set up a wider cleaning platform so that large-scale equipment can be used for cleaning. The horizontal transport platform c and the inclined transport platform d are determined in accordance with the transport route in which the development system is arranged. Their width depends on the type of transport equipment, specifications and number of lines. See Table 8-2, 8-3, and 8-4 for the minimum width of the open pit transportation platform.

Table 8-2 Minimum width of open-pit mine quasi-rail railway transport platform (m)

Table 8-3 Minimum width of narrow-gauge railway transport platform for metal open pit mine (m)

Table 8-4 Minimum width of the transport platform (m)

The final step slope angle is related to the nature of the rock, the inclination, inclination, structure, joints, and methods of penetration. For example, when the rock slope is greater than 30° and the rock bedding is more developed, if the selected step slope angle is greater than the rock slope, the rock will slip easily. At this time, the slope angle of the step should be taken to be equal to the inclination angle of the rock formation. See Table 8-5 for the final step slope angle data generally used in open pit mine design.

Table 8-5 Step Slope Angle Reference

After the various platforms are determined, the final slope angle of the open pit mine can be calculated as follows

Where β is the final slope angle, (°);

n - the number of steps;

H——step height, m;

Α——step slope angle, (°);

a - the width of the safety platform, m;

B——the width of the cleaning platform, m;

C——the width of the horizontal transport platform, m;

d - the width of the inclined transport platform, m.

n ₁ , n ₂ , n ₃ , n ₄ - the number of safety platforms, sweeping platforms, horizontal transport platforms and inclined transport platforms, respectively.

The minimum slope angle determined by the above safety conditions and technical conditions is the final slope angle of the open pit mine. However, for a gently inclined ore body, if the slope angle is greater than the inclination angle of the ore body, the final slope angle should be arranged along the lower part of the ore body to fully extract the ore. As shown in Figure 8-2-10, cd should be used as the boundary line, but not cd'.

Figure 8-2-10 Slope angle of the lower inclined ore body

See Table 8-6 for the composition of the final slope of some open-pit mines in China, and Table 8-7 for the information of the slopes of some open-pit mines abroad.

Table 8-7 Data of some open-pit mine slopes in foreign countries

Table 8-6 Composition of the final slope of some open pit mines in China

c) Determine the depth of open pit mining

1. Determination of mining depth in long open pit mine

When the length of the open pit mine is large, the mining depth is initially determined on the cross-sectional profile of each area, and then the vertical section is used to adjust the bottom elevation of the open pit.

(1) Initially determine the depth of open pit mining on the cross-section of each region

First, several depth mining prospects are made on each cross-sectional view (Fig. 8-2-11). When the burial conditions of the ore body are simple, the depth scheme is less; when the ore body is complex, the depth scheme takes more, and must include the depth of the boundary stripping ratio that has a significant change. When drawing the realm, according to the minimum bottom width and slope angle selected in the front, pay attention to the open bottom.

In the position in the ore body, it is also necessary to identify whether the slope angle on the cross-sectional view is actual or pseudo-tilt. If it is a pseudo-tilt, then

Need to be converted.

Secondly, for each depth scheme, the area ratio method (Fig. 8-2-11 scheme H ₁ > or line segment ratio method (Fig. 8-2-11 scheme H _{3) is} used to calculate the boundary stripping ratio.

Finally, the boundary stripping ratio of each scheme is plotted with the mining depth (Fig. 8-2-12), and then the horizontal line representing the economic reasonable stripping ratio is drawn. The abscissa Hj of the intersection of the two lines is required. Mining depth.

Figure 8-2-11 Determination of mining depth in long open pit mine Figure 8-2-12 Relationship between stripping ratio and depth in realm

So far, the determination of the theoretical depth of open pit mining on a geological cross-section has been completed. In the same way, the theoretical depth on all cross-sectional views in the open pit mine can be determined.

It should be pointed out that in determining the mining depth of thick ore bodies, in view of the difficulty in determining the position of the open pit bottom, sometimes the drawing is based on the thickness of the ore body rather than the minimum bottom width (Fig. 8-2-13), and then continues to be stripped downward. Mining until the minimum base width. At this time, the final depth of open pit mining is obviously the sum of the initially determined depth and the non-peeling mining depth.

Figure 8-2-13 Non-peeling mining of thick ore bodies

H1-originally determined depth of mining; H2-depth without stripping

H-final open pit depth

<2> Adjusting the bottom elevation of the open pit mine on the geological longitudinal section

After preliminarily determining the theoretical depth of open pit mining on each geological cross-section, the resulting mining depth is different due to the variation of ore body thickness and topography. Project the depth on each profile onto the geological longitudinal profile and connect the points to produce an irregular polyline (dashed line in Figure 8-2-14).

Figure 8-2-14 Adjusting the elevation of the open bottom plane on the geological longitudinal section

The dotted line is the mining depth before adjustment; the solid line is the adjusted mining depth

In order to facilitate the mining and layout of transport routes, the bottom plane of the open pit mine should be adjusted to the same elevation. When the burial depth of the ore body changes greatly along the strike, and the length allows, the bottom plane can be adjusted to be stepped. The principle of adjustment is to make the amount of ore mined less than the amount of ore mined, and to make the stripping ratio as small as possible. The solid line in Figure 8-2-14 is the adjusted design depth.

2. Determination of mining depth in short open pit mine

For the open pit mines that are short, it is necessary to fully consider the influence of the amount of rock removed from the end. When determining the depth of exploitation, consider the open pit mine as a whole with a plan view. The specific steps are as follows:

(1) According to the shape of the ore body and the determined economically reasonable stripping ratio, several possible depth schemes H ₁ , H ₂ , H ₃ , ..., etc. are selected;

(2) For each depth scheme, draw the bottom perimeter D of the level on the corresponding layered plan, according to the selected minimum base width and with reference to the shape of the ore body (Fig. 8-2-15a);

Figure 8-2-15 Determination of mining depth in short open pit mine

(a) plan view; (b) sectional view of the IV survey line; (c) 1-1 'auxiliary section view

<3> On the same floor plan, the vertical projection S of the perimeter boundary L of the open pit and the contact line of the ore on the slope is further determined. On each cross-section and longitudinal section, the slope line is selected according to the selected slope angle (Fig. 8-2-15b), and the intersection of each slope line with the topography and the ore contact line is found, and then projected to On the layered plan (points a, b, c, f on the graph). In the case where there is no section, on the layered plan, select the representative points as the auxiliary section perpendicular to the bottom perimeter (1-1' in Fig. 8-2-15c), and then draw on the auxiliary section Exit the slope line and find the intersection of it with the topographic line and the contact line of the rock, and then project it onto the layered plan. Finally, the projection points of the cross section, the longitudinal section and the auxiliary section are connected, that is, the vertical projection of the contact line of the ore on the perimeter and the slope of the open pit;

(4) Calculate the boundary stripping ratio n _j1 , n _j2 , n _j3 , ... of each depth scheme according to the plan method;

(5) Draw the boundary stripping ratio, the relationship between n _{j and} depth H, and find the depth of the stripping ratio of the boundary equal to the economically reasonable stripping ratio. This depth is the reasonable depth of exploitation of open pit mines.

d) draw the bottom perimeter of the open pit mine

Whether it is a long open pit mine or a short open pit mine, the adjusted depth of exploitation is often no longer the depth of the original plan, so the bottom perimeter needs to be redrawn, as shown in Figure 8-2-16. The steps are:

Figure 8-2-16 Determination of the bottom perimeter

Theoretical perimeter; design perimeter; F1, F2—fault

(1) Draw a geological layer plan of this level according to the adjusted open pit depth;

(2) plot the boundary according to the determined open pit depth on each cross section, longitudinal section and auxiliary section view;

(3) Projecting the perimeter of the open bottom of each open section to the layered plan, connecting the points to obtain the theoretical bottom perimeter (dashed line on Figure 8-2-16);

(4) In order to facilitate the mining and transportation, the theoretical boundary drawn from the preliminary need to be further trimmed. The principle of trimming is:

1) The bottom perimeter should be as straight as possible, and the curved part should meet the requirements of the transport equipment for the radius of curvature;

2) The length of the open pit mine should meet the requirements of the transport route, especially the mines that are transported by rail. The length of the mine should ensure that the train enters the working face normally.

The bottom perimeter thus obtained is the final design perimeter, as shown by the solid line in Figure 8-2-16.

V) Drawing the end plan of open pit mining

The method for drawing the end plan of open pit mining is:

(1) The perimeter of the bottom of the above open pit mine is painted on transparent paper.

(2) Cover the topographic map with transparent paper, and then start the bottom perimeter of the slope according to the composition of the slope, and draw the bottom line of each step from the inside to the outside (Fig. 8-2-17). It is obvious that the bottom line of each step in the deep part of the open pit mine is closed in plan view, while the ground level above is not closed, but the end is to be closely connected with the topographic contour line of the same elevation.

(3) Arrange the development of transportation routes on the map.

(4) Starting at the bottom perimeter, the slopes and platforms of each step are drawn from the inside to the outside (Fig. 8-2-18). When drawing, pay attention to the connection between the inclined transport lane and each step. When delineating various levels, the ore body boundary should be checked frequently with geological transverse, longitudinal and stratified plans so that the amount of ore is less and the amount of rock is less in the bound range. In addition, the perimeter of each level must meet the requirements of transportation work.

Figure 8-2-17 The preliminary plan for the open pit mining

When the mining scheme is simple or the design technology is mature, the above steps 2, 3, and 4 can be combined, that is, after drawing the bottom perimeter of the open pit mine, according to the selected pioneering transportation mode and the position of the entrance and exit, draw out from the inside out. The platform and slope of each step, once painted the end plan of the open pit mining.

(5) Examine and revise the above-mentioned open-pit mining boundary. Since the original open-pit mining boundary is often affected by the development of transport routes during the mapping process, it is necessary to recalculate the boundary stripping ratio and the average stripping ratio to check whether they are reasonable. If the difference is too big, it is necessary to re-determine the realm. In addition, the above realm should be modified according to specific conditions. For example, when there are mountains and high mountains in the realm, in order to greatly reduce the stripping ratio, it is necessary to avoid the high mountain parts; for example, when there are not many remaining minerals outside the realm, if all the mining increases the stripping ratio, If it is not large, it is advisable to expand the realm and use all open pit mining.

In short, the determination of the open-pit mining realm is a complex subject. In the design work, it is necessary to follow the basic principles, and to adapt to specific conditions in a flexible and flexible manner, so that the realm is determined more rationally. It should be pointed out that what is described in this section refers to the determination of the known boundary of the ore body surrounding the rock boundary. Usually the mining boundary of iron ore deposits is determined in this way. However, for disseminated copper ore deposits and the like, it is not obvious boundaries of ore and rock, sometimes realm delineated topics and determine the cut-off grade integrated together. As the grade of the boundary changes, the boundary between the ore body and the surrounding rock and the amount of ore will also change, and the open-pit mining boundary will be different. For a certain cut-off grade, since the ore body boundary and ore reserves have been given relative, the method for determining the boundary is as described in this section. However, this realm is not necessarily the final state of adoption. It still needs to be combined with the cut-off grade to measure the economic effects of mining.

It should be pointed out that the above methods all determine the mining depth on several geological profiles selected, and accordingly define the open-pit mining boundary. Although this method of determining the open-pit mining boundary is still widely used, since the selected section does not necessarily have a vertical open-pit mine slope, the upper intersection angle and the deep intersection angle are different, and the phenomenon of the intersection angle of the upper disc and the lower disc is not uncommon. Therefore, using the area of ​​the ore rock on the sectional map to simulate the true stripping ratio sometimes produces a large error, so it is often difficult to obtain economically optimal results in the determined open-pit mining boundary. The method developed by means of the deposit model and the electronic computer program to determine the open-pit mining boundary can be the method for determining the optimal stope boundary.