What are the final elements of the open pit stop?

The final elements of the open pit are as follows:

1. Factors affecting the final side of the stope to help stabilize

The final side of the open pit mine is composed of stage height, stage slope angle and cleaning platform, safety platform and transportation platform. The main factors affecting the final side of the stability are:

(1) Physical and mechanical properties of rock: including rock hardness, cohesion and internal friction angle, etc.

(2) Geological structure: including weak surfaces composed of fracture zones, faults, joint fissures and bedding planes, unstable soft rock interlayers, and soft rock expansive to water;

(3) Hydrogeological conditions: static pressure and dynamic pressure of groundwater, influence of groundwater activity on rock formation stability;

(4) The impact of earthquakes in strong earthquake zones,

(5) The technical conditions of mining and the time of existence of the side help.

In order to ensure the stability of the final side of the stope, the formation of the side help can generally take the following technical measures:

(1) The 1~2 row of blastholes near the final side gang are controlled by blasting, smooth blasting, and encrypted hole spacing. The Daye iron ore using a hole pitch of 3m blasting network (Blasting normal pitch of 4 ~ 5m, pore diameter 170mm).

(2) Reduce the amount of charge in the blasthole, and use differential blasting to reduce the vibration of the blasting side.

(3) Specialized dewatering work for mines with complex hydrogeology.

2, the final help angle

The final slope angle of the open pit is the angle between the imaginary plane and the horizontal plane formed by the bottom line of the last stage of the stope and the top line of the last stage (see Figure 1-1-1).

The final slope angle should be determined according to the rock properties, geological structure and hydrogeological conditions of the side gang, and considering the safety and stability factors and the requirements of arranging the transportation system. In order to reduce the amount of peeling, the final side angle should be as large as possible while ensuring the production needs and safety.

When preparing a design task book or feasibility study, the final slope angle can be selected by reference to the actual data of similar mines or the data of the design department.

When the preliminary design is prepared, the mines with simple geological conditions in small and medium-sized mines and slopes can be calculated according to the preliminary physical and mechanical properties of the mine rock, or the final slope angle can be selected by referring to the actual data of similar mines. For large mines and mines with complex geological conditions, prior to preliminary design, the relevant departments should be entrusted to carry out systematic research on the stability of the side, and the slope stability study report and recommended slope angle values ​​should be used as the design. Basis. If the research report is submitted after the preliminary design is completed, the design department should check and correct the side design in the construction drawing design.

3, stage deviation and stage slope angle

(1) The stage height depends mainly on the nature of the rock and the loading equipment specifications.

For soft rock that does not need to be worn loose, the stage height generally does not exceed the maximum excavation height of the excavator.

For hard rock that needs to be worn loose, the stage height does not exceed 1.25 times the maximum excavation height of the excavator.

In the open pit mines designed and produced in China, the stage height of small mines is generally 8~10 m, and that of large and medium-sized mines is generally 10~12m. When the large open pit mine uses an excavator with a bucket capacity of 8 m ³ or more, the stage height can be 12-15.

If the rock formations that make up the final side gang are better and allow steeper sloping angles, consider combining two or three stages into one high stage.

(2) The slope angle of the stage is related to the nature of the rock, the dip angle and inclination of the rock formation, the joints, the bedding and faults, the stage deviation and the method of piercing and blasting.

4, the final platform width

The final platform of the open pit is divided into a safety platform, a cleaning platform and a transportation platform.

The width of the safety platform and the cleaning platform have a certain geometric relationship with the final stop angle of the stope, which can generally be determined by calculation. That is, the average width of the platform is calculated first, and then the platform is composed to determine the width of the safety platform and the cleaning platform.