Loading work

Mining work is the work of using mining equipment to extract ore rock from the ore pile in whole or broken by blasting, and load it into a transport container and transport it to the receiving bunker of the crusher or a certain location.

The

machinery and equipment used in the collection and assembly work include excavators, electric shovels, loaders, etc. Due to the relatively hard rock of metal mines, excavators and electric shovels are mainly used in production.

     The main working parameters of the excavator include the following aspects:

(1) Excavation radius: the horizontal distance from the center of the excavator to the tip of the bucket tooth during excavation.

Maximum excavator radius: The digging radius when the stick is extended horizontally at its maximum.

Standing Horizontal Digging Radius: The digging radius where the bucket is laid flat on the standing level.

(2) Excavation height: the vertical distance between the tip of the bucket teeth and the standing horizontal.

Maximum digging height: The vertical distance between the tip of the bucket teeth and the standing horizon when the stick is most extended and raised to the highest position.

(3) Discharge radius: the horizontal distance from the center of the excavator to the center of the bucket during unloading.

Maximum Dump Radius: The unloading radius when the stick extends most horizontally.

(4) Unloading height: the vertical distance from the lower edge of the bucket from the standing horizontal.

Maximum unloading height

: The unloading height of the stick that extends the maximum and mentions the highest position.

Digging Depth: The vertical distance between the tip of the bucket teeth and the standing level when the bucket is digging down.

     How the excavator works

(1) Normal pile blasting operation mode

In the loading operation of

open-pit mine, according to the relative position of the transportation equipment and the excavator, the loading operation mode is divided into three types: flat loader, upper loading truck and combined loading.

A  flat loading truck

The excavator is located on the same level as the transport equipment.

B  Loading on the vehicle

The transport equipment and the excavator are located on the upper and lower levels of the steps.

C  Joint loading

The transport equipment is located on a flat plate in the middle of the steps.

In actual production, flat loading trucks are most commonly used.

(2) Special collection and assembly operation methods

When the ore body structure is complex, there are many rock interlayers in the ore body, or there are a variety of different grades of ore in the

deposit, in order to meet the requirements of product quality and grade, and minimize the loss and dilution of ore, special mining methods must be adopted in the loading process to achieve the separation of different grades of ore and interlayer rock.

Zone A  blasting

When different types and grades of ore are deposited in the horizontal direction of the step, or when there is contact between ore and rock junction

in the horizontal direction of the step, it can be divided into small areas according to the ore type, grade or ore-rock junction, and blasting and mining can be carried out separately. As shown in the figure below, zone I is rock, zone II is ore, first blasting mining area II. and then blasting mining and loading area I. to minimize ore loss.

B-section  blasting and packing

When there is a local ore (or rock)

layer in the vertical direction of the step, according to its occurrence depth, the method of segmented blasting is adopted, and after blasting, this part of the ore (or rock) is loaded and transported away by excavator.

C  Layered packaging

When mining a gently inclined or horizontal group of thin ore bodies, the entire step can be divided into two or more steps according to the ore contact line for layered mining.

First, blast up part of the steps, and then, from the lower flat plate pad a gentle passage to the upper part of the steps for the excavator to walk up and down. When the upper part of the steps is advanced to a certain distance and the lower part of the steps is exposed to a certain area, the perforation and blasting of the lower steps can begin. At this time, the work is carried out simultaneously on the upper and lower steps. After the lower step is blasted, the excavator returns and loads the lower part of the step while perforating and blasting the upper step.

This method of operation minimizes ore loss and dilution, guaranteeing the supply of different grades of qualified ore. However, it is necessary to set up a gentle passage up and down steps, and the excavator goes up and down frequently, and the effective operation time is reduced.

     Determination of excavator production capacity and quantity

Excavator production capacity refers to the volume or tonnage of solid ore rock loaded from the face into a transport container in a calculated unit of time. There are generally two types of comparative methods and analytical calculation methods for determining production capacity.

A  Contrasting method

The contrast method is often used in the development of mine stripping plans and the design of new mines.

For mines in production, when formulating the mining and stripping plan, the excavator production capacity can be determined according to the actual statistics of the excavator production capacity of the mine in recent years, and combined with the comparative analysis of the specific production conditions, and consider the indicators that may be achieved after taking measures.

For new mines, generally theoretical calculations should be made first, and then selected with reference to the production capacity of other mining excavators with similar conditions. Since the natural conditions of each mine cannot be exactly the same, when selecting other mine indicators, attention should be paid to analyzing the specific situation, such as hillside open-pit and deep concave open-pit water, transportation mode, ore properties, equipment maintenance, driver operation technology level, production organization management level, etc.

B  Analytical calculations

a  Technical production capacity

Technical production capacity

refers to the production capacity that can be achieved by an excavator under the technical conditions of a specific mine (working face size, ore rock properties, loading conditions, etc.). This takes into account the degree of bucket filling, the coefficient of ore looseness and the working cycle time, and the production capacity of continuous operation is the maximum production capacity that can be achieved after taking measures.

Technical production capacity Qj(m³/h) = 3600 * excavator bucket volume E * solid full bucket coefficient K÷ excavator cycle time t(s).

Among them: the solid full bucket coefficient K = the volume V of the solid ore rock ÷ (the total number of buckets N * the bucket volume E).

b  Working capacity

The working capacity takes into account the impact of blasting, transportation, equipment maintenance and other aspects in the actual work of the mine, that is, the time utilization coefficient is considered.

Excavator single shift production capacity Qb(m³/set · shift).

= Technical production capacity Qj * shift working hours T * shoveling working hours accounted for the proportion of shift work η

 The number of excavators required for the mine N = annual stripping capacity A÷ excavator annual efficiency Qa

Excavators equipped with open-pit production do not consider the spare quantity, and if the working system of mining and stripping operations is different, the equipment models are different, and the production efficiency is different, the number of excavators required for mining and stripping operations can be calculated separately. In addition, if the mine has other projects, such as road construction, road finishing, slope and dumping, etc., you can also consider having loaders, graders, bulldozers, etc.

     Ways to increase the production potential of excavators

The total capacity of the

total excavator of the whole mine is the total amount of mine stripping, so the excavator production capacity is a very important technical and economic indicator. Giving full play to the excavator's capabilities is directly related to ensuring or exceeding the mine's planned stripping volume.

The factors

affecting the production capacity of excavators are many, and this article mainly discusses the technical influencing factors after the selection of excavators and the ways to improve the capabilities.

A  Shorten the loading cycle time

The time required for one operation cycle of the excavator is the sum of the four steps of excavation loading T1, full bucket rotation T2, unloading T3, and empty bucket rotation T4 to the working face. Namely:

Loading work cycle time T = Backhoe loading t1 + full bucket rotation t2 + unloading t3 + air bucket rotation t4

The working cycle time is related to the nature of the shoveled ore, the quality of ore blasting and crushing, the parking position of the vehicle, the loading swing angle and the driver's operating technical level. Among them, increasing the swing speed and reducing the swing time are of great significance to shorten the working cycle time. The driver can reduce the shoveling resistance by using a reasonable shoveling sequence, that is, shoveling from the outside to the inside, from the bottom up, and the driver can use the waiting time to clean up the working face, and pour the ore rock of the working face to a position close to the parking of the car, so that the rotation angle of the excavator is not more than 90°, and the working cycle time can also be effectively shortened.

B  Increase the digging bucket coefficient K

The excavation coefficient is calculated by the full bucket coefficient and the loose coefficient, which is the ratio of the volume of loose

ore rock dug into the bucket to the bucket volume, which is related to the properties of the ore rock, the degree of blasting block and the operation technology, the most important of which is the degree of blasting block. When the blast pile is scattered and there are more large blocks and roots, the working cycle time of the excavator increases and the full bucket coefficient decreases.

Reducing the block rate mainly starts from two aspects, one is to improve the blasting quality, and the other is to choose a large-sized digging bucket. By adjusting the blasting parameters, selecting a reasonable charge structure, adopting multi-row hole differential blasting, appropriately increasing the single consumption of explosives, etc., the unqualified bulk and root are reduced, so that the shape and size of the blasting pile after blasting are conducive to the safe and efficient operation of the excavator.
C  Improve the η utilization factor of class working hours

D  Timely supply of empty vehicles to the work face

The intelligent vehicle scheduling system can be adopted to reasonably organize and reasonably allocate transportation lines, improve vehicle entry and replacement conditions, and reduce the time for excavators to wait for vehicles.

 

 

     Transportation work

Open-pit mine transportation is one of the main production processes of the mining process by transporting the extracted ore out of the stope and to the designated unloading point, transporting the stripped material to the dumping site, and sending production personnel, equipment and materials to the work site. The investment in the transportation system accounts for about 40%~60% of the total investment of the mine, and the transportation cost accounts for about 30%~40% of the ore cost. Therefore, the rationality of the transportation mode and system of open-pit mine directly affects the economic benefits of open-pit mine production.

Due to space limitations, this article only discusses the calculation of transportation capacity and vehicle selection using dump truck transportation mode.

 

     Transportation capacity calculation

The main factors affecting the production capacity of automobile shifts are load capacity, transportation cycle and shift working hours.

Automobile shift production capacity A (tons

/ shift) = 60 * car load capacity q (tons) * shift working time T (hours) * automobile load factor K1 * automobile working time coefficient η÷ automobile transportation cycle t (minutes).

Number of registered cars N = automobile transportation imbalance coefficient K2 * mine class output Qb÷ (automobile class production capacity A * vehicle production rate K3).

     Ways to improve vehicle efficiency

A  Improve road conditions

According to statistics, every 1km/h increase in vehicle speed can improve vehicle efficiency by about 4%~8%.

B  Strengthen production management and reduce auxiliary operation time and non-operation time

According to statistics, under normal circumstances, the time necessary for shift handover and personal is 8%~10%, the round trip to and from the warehouse and mine accounts for about 3%, the car refueling accounts for 3%~5%, and the operation time accounts for 82%~86%.

In order to reduce the idle travel time and non-operation time of production vehicles, gas stations should be located at the places where ore trucks pass to and from; The temporary inspection and maintenance site should be close to the transportation trunk line of the stope; In the cold areas of the north, maintenance vehicles (one guarantee, temporary inspection) should have a maintenance warehouse. Regular maintenance and overhaul of automobiles should be strengthened to improve vehicle uptime.

C  Strengthen the cooperation with the shovel equipment to improve the supply conditions

D  Strengthen vehicle dispatch

     Car selection

After the tonnage of the car is determined, it is necessary to choose a specific model. There are many factors affecting the selection of open-pit dump trucks, the most important of which are the annual transportation volume, transportation distance, road technical conditions and bucket capacity specifications of loading equipment.

The selection of models should consider the quality of the car, reliable work, reasonable structure, advanced technology, stable quality, low energy consumption and other conditions, as well as the strength of the cabin suitable for the punching of large pieces of ore. When there are multiple models to choose from, technical and economic comparisons should be made, the optimal model should be recommended, and the same model of car should be selected as far as possible in the same open-pit mine. In terms of costs, it is necessary to consider not only the purchase price of the new car, but also the operating costs after production, warranty costs and spare parts prices, and the supply of spare parts.

For mines with large annual transportation volume and short transportation distance, generally choose a vehicle with a heavy load, with an annual transportation capacity of 80 million ~ 100 million tons, and the use of a 150-ton truck can basically be completed; On the contrary, you should choose a car with a small load, and oversized models must be equipped with larger procurement equipment, increasing excessive investment.

     Selection of new energy models

Mines have sufficient power supply, and most of them are heavy-duty downhill transportation, you can consider choosing to charge mining wide-body dump trucks.

There is a natural gas supply near the mining area, and you can consider choosing a wide-body dump truck for natural gas extended range mining.

     Application prospect of unmanned mining wide-body dump truck

In accordance with the overall design requirements of the Ministry of Industry and Information Technology's "Guidelines for the Construction of Intelligent Mines in the Nonferrous Metals Industry" (for trial implementation), mines are encouraged to adopt cloud, edge and end architectures based on industrial Internet platforms, establish a full-process intelligent production control system for "ore flow", gradually promote the construction of intelligent mines in enterprises, and finally realize the unmanned production of the whole process of mines.

For existing mines, carry out digital and intelligent transformation of equipment, carry out complete sets of intelligent equipment applications, and realize intelligent diagnosis of equipment faults, optimization of process parameters, optimization of production processes, optimization of digital simulation, and optimization of business decisions; At the same time, the construction of mine intelligent production system is carried out to realize the digitalization of resources, intelligent control of production process, and integrated safety management.