Design Principle of Underground Mining Dump Truck

Abstract：Underground ore truck and open-pit dump truck are of mine dump truck but their work conditions are quite different, therefore the design principles of both trucks are not the same .This paper discussed the differences between both trucks in purification of exhaust gas determination of general structure and parameters and arrangement of mechanism etc.and further clarified the principle of design of underground ore truck.

Key Words：Mine truck, Work condition, Design principle, Parameters determination

Underground truck is the key equipment to realize trackless mining operation in underground mine. Its application plays an extremely important role in simplifying mining technology and improving mine production capacity. It plays an important role in underground mining because of its remarkable characteristics such as 6.0 ~ 28 m3 body volume, 12 ~ 60 t loading capacity, high mobility and flexibility.

There are many similarities between underground mining trucks and surface mining dump trucks, such as having the front and its hydraulic lifting mechanism, the transmission system of diesel engine torque converter power shift gearbox drive axle, and similar working hydraulic system and braking system. However, due to their different working environment, their design principles are different. This paper focuses on the differences between the two from the working environment, the purification of waste gas, the determination of overall parameters, the arrangement of mechanism, etc., and then expounds the design principles of underground mining trucks.

1. Difference between Underground Mining Dump Truck and Open Pit Mining Dump Truck

Due to the different working environment of underground mining dump truck and open-pit mining dump truck, there are essential differences in mechanism layout and determination of overall structural parameters between them.

1.1 Different Dimensions and Driving Modes

1.1.1 Overall dimension. Open pit dump truck is responsible for transporting ore from open pit stope to ore bin of concentrator. The transportation route is from the stope to the ore dressing plant bin, and the running road condition is worse than the general road condition. However, the requirements for the external dimensions of open-pit mining dump trucks are not strict. Therefore, open-pit mining dump trucks generally use integral frame, and the external dimensions of vehicles are larger than those of underground trucks with the same tonnage.

Underground mining truck is used to transport ore in the underground roadway, and its working conditions are very different from those of open-pit mining dump truck. Most narrow roadways are single lane, and the width of the lane is the width of the roadway. Therefore, the overall size of underground mining truck is strictly limited by the roadway specifications, and the vehicle inevitably adopts articulated body structure, In order to get a smaller turning radius.

Statistics show that the width and height of open-pit dump trucks are larger than those of underground trucks with the same tonnage, but the length of the latter is longer than that of the former. The working environment restricts the underground trucks to adopt low and narrow body structure.

1.1.2 Driving form. Open pit mining dump truck can be divided into two types of structure: two axle type and three axle type. At present, open pit mining dump truck at home and abroad generally adopts two axle rear dump truck. Although the two axle truck can be four-wheel drive, it is usually only rear wheel drive and front axle steering. However, 94% of underground mining dump trucks are of double axle structure, and only 6% of them are of three axle structure. Most underground mining trucks adopt hydro mechanical transmission mode. Because the underground mining trucks all adopt articulated body structure, and the front middle (rear) axle double axle drive form, this can make full use of the attached weight of underground mining dump trucks, and improve the passing capacity of vehicles under the condition of uneven road.

1.2 Different Requirements for Waste Gas Purification

Open pit mining dump truck is used for open pit operation. This kind of dump truck mostly adopts the direct injection engine (diesel engine) with the characteristics of low heat load, high average effective pressure and low fuel consumption, so the exhaust gas from the engine is generally discharged into the atmosphere directly after passing through the muffler. Therefore, its exhaust emission and purification is not a prominent problem.

Underground mining trucks are generally powered by diesel engines. When diesel engine works underground, the problem of exhaust gas purification must be solved first. Diesel engine exhaust contains carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (CH) and other toxic substances harmful to human health. Therefore, the relevant countries have made strict regulations on the exhaust emission standards of diesel engines used underground.

2. Design Principle of Underground Ore Truck

The power sources of underground mining trucks are diesel engines, batteries or overhead cables. Although the production capacity of electric underground mining trucks is 7% ～ 42% higher than that of diesel mining trucks, due to the particularity of power sources, there are few users in the world. Most underground mining trucks are still powered by diesel engines, The following focuses on the design principles of diesel underground mining truck

2.1 Reasonable Determination of Diesel Engine Power

2.1.1 Determine the power of diesel engine on the premise of reducing the total amount of exhaust emissions. Low pollution diesel engine is used to reduce the content of harmful substances in the exhaust gas, and the method of external catalytic box purification is adopted to make the emission index of harmful substances of diesel engine meet the requirements of underground operation. However, with the increase of the truck weight (container capacity), the power of diesel engine is bound to increase, so the total emission of harmful substances will increase with the increase of the total emission of exhaust gas. According to the relevant data, the exhaust emission of Deutz air-cooled diesel engine will increase by 1.38-1.44 L / kW, so it is necessary to increase the ventilation in the underground tunnel to eliminate the harm of the sudden increase of the total emission of CO, CH, NOx and other toxic and harmful gases. Therefore, it is necessary to determine the power of underground mining truck reasonably on the premise of reducing the total exhaust emission under the condition of meeting the operation requirements of underground mining truck. The research shows that the diesel engine power of underground mining truck is smaller than that of open-pit mining dump truck under the same effective load. Therefore, it is an important guiding principle for the design of underground mining truck to seriously consider the harm of waste gas and not copy the engine power of open-pit mining dump truck from the Perspective of minimizing the total emission of waste gas.

2.1.2 Ensure enough traction and reasonably determine the power of diesel engine. Traction force is one of the most important technical parameters of underground mining truck. The ultimate tractive force of a vehicle mainly depends on the weight of the vehicle and the adhesion coefficient of the road. The self weight utilization coefficient η G 0 of surface mining dump truck with load capacity of 150-450 kn is generally between 1.1-1.5. Therefore, according to the requirements of traction and climbing ability of underground mining truck on site operation conditions, reasonably determining the diesel engine power of underground mining truck is another design guiding principle of underground mining truck.

2.2 Reasonably Determine the Speed According to the Underground Operation Conditions

The running speed of underground mining truck directly reflects its running efficiency. The attached table shows the comparison between the load and the maximum speed of underground mining truck at home and abroad. It can be seen from the attached table that with the increase of load, the speed of underground mining truck tends to increase in order to improve its comprehensive efficiency, but the maximum speed of most underground mining trucks is far lower than that of open-pit mining dump trucks, People concerned think that the speed of underground mining trucks running on the rock road should be 6-10 km / h. in the wide main transport roadway on the cement road, the speed can be increased to about 15 km / h. This is mainly due to the specification of underground roadway, The uneven road surface with muddy water, poor lighting, sharp curves and poor driver's field of vision have strict constraints on the speed of underground mining trucks. The appropriate speed can ensure the safe driving and no ore scattering of the underground ore truck.

2.3 Overall Dimensions of Underground Ore Truck

Underground mining trucks often have multiple loading points, and most of the roadways they run are single lanes. The width of the carriageway is basically the width of the roadway, and the safety gap between the mining trucks and the roadways is very small. Therefore, the underground operation conditions put forward strict requirements on the length, width and height of the underground mining trucks. Due to the constraints of the working conditions of the underground transportation roadway, the underground transportation truck adopts a low and narrow car body structure. At the same time, in order to adapt to the rough conditions of the underground roadway, in addition to the hinged structure, the designer must also consider adding a vertical swing mechanism to make the driving wheel always touch the ground, increase the attachment weight, and improve the passing capacity of the vehicle.

2.4 Layout of Cab

In the vast majority of underground tunnels, underground transport trucks can not turn 180 ° in place and then run. Therefore, the driver's cab is mostly arranged on the left side of the car body, and the driver can sit side by side. He only needs to slightly deflect his head to observe and operate back and forth. Moreover, the driver's cab is located in the front frame, far away from the ore pass, which is conducive to the safety and health of the driver. There are also some underground mining trucks using the dual steering wheel two-way frame driving scheme, the driver just need to turn the driver's seat to achieve two-way driving.

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