There are three main haulage systems that are used in hard rock open pit mines. These are:
- Conventional truck haulage
- Truck trolley systems
- In-pit crushing and conveying (IPCC)
What is the mine’s current haulage system?
The most common mine haulage system transports all the blasted material by conventional, off road trucks. The ore is transported to the crusher, from where it is transported to the processing plant by conveyor belt. This either a surface conveyor, or a conveyor tunnel. All the waste is transported by conventional trucks to one of the waste dumps. A schematic representation of the mine’s current haulage system is given below (copper mine used as an example).
1. Conventional truck haulage
Off-highway trucks have established themselves as the primary means by which both ore and waste are moved in large open pit mines. Trucks are being loaded by a shovel, after which they drive either to the waste dump or to the processing site/in-pit crusher. The loading and hauling equipment should be matched to ensure the optimal amount of fill cycles for the shovel. Mining haulage trucks exist in all kinds of capacities up to 450 tonnes. An example of a conventional truck is the Caterpillar 795F AC with a payload of 313 tonnes and is shown in the figure below.
Are environmental regulations, health and safety concerns or potential profit loss a concern right now?
The advantages and disadvantages of conventional truck haulage are listed below.
| Advantages | Disadvantages |
| High flexibility and reliability | High operational costs |
| Low capital costs | Labor intensive |
| Compatible with all types of materials | Mine roads need to be maintained |
| Possibility to mine selectively | Inefficiency due to travelling of empty trucks |
| Outsourcing is possible | High level of diesel emissions |
2. Truck trolley system
The use of truck trolley systems dates to 1882, when Werner von Siemens developed the first electrical driven wagon that followed overhead power lines. This system has been evolving since and has been used in the mining industry since 1967, when it was implemented in the Chino Mine in New Mexico. Due to the lack of large trolley equipment, the truck trolley system has never been widely used. However, the interest revived again when Caterpillar introduced their first diesel-electric truck in 2006 with a payload of 345 tonnes. A schematic of the trolley assist system is shown below.
The advantages and disadvantages of truck trolley systems are listed below.
| Advantages | Disadvantages |
| High flexibility and reliability | High operational costs |
| Low capital costs | Labor intensive |
| Compatible with all types of material | Mine roads need to be maintained |
| Possibility to mine selectivity | Inefficiency due to travelling empty trucks |
| Less emissions due to the substitution of diesel fuel with electricity | Extra investment due to the installment of the trolley line system |
| Higher uphill speed which leads to shorter cycle times | |
| Extension of interval between engine overhauls |
3. In-pit crushing and conveying
IPCC systems consist of the application of a fully mobile, semi-mobile or fixed-in-pit primary crusher, which is coupled to a conveyor system. IPCC systems could lead to the partial or complete substitute for trucks because of their lower operating, maintenance and energy costs for conveyors. There are five possible conveying systems:
- In-pit conveyor
- Conveyor tunnel
- High angle conveyor
- Skip conveying system
- Trucklift
3.1 In-pit conveyor
An in-pit conveyor system is the most basic system. The conveyor belt will either follow the ramp upwards or will have an incline along the pit wall. It will continue until it reaches the processing plant, or a transfer station that has a connection to the processing plant. The advantages and disadvantages of an in-pit conveyor are listed below.
| Advantages | Disadvantages |
| Less power installed than with conventional truck haulage | High capital investment |
| Less labor intensive than conventional truck haulage | The depth of mine requires a very long conveyor belt |
| Less gas emissions than conventional truck haulage | Non-flexible |
| Less road maintenance | |
| Less dust, noise, and water usage | |
| Less maintenance than conventional truck haulage | |
| Long lifetime up to 60 years |
3.2 Conveyor tunnel
The tunnels are drilled by tunnel boring machines and afterwards an overland conveyor belt is installed. The tunnels have a cross section of 35 to 51 meters and maximum angle of these tunnels is 15 degrees, although 12 degrees is more favorable because of the easier maintenance of the belts. The advantages and disadvantages of conveyor tunnel are listed below.
| Advantages | Disadvantages |
| Not climate dependent | Tunnel must be drilled |
| Easy and cheap maintenance | Long tunnel is required |
| Less power installed than with conventional truck haulage | Expensive initial investment |
| Less labor intensive than conventional truck haulage | |
| Less gas emissions than conventional truck haulage | |
| Less road maintenance | |
| Less dust, noise, and water usage | |
| In-house knowledge is already available |
3.3 High angle conveyor
A high angle conveyor (HAC) is getting more popular in the mining industry. It is currently successfully used in the tunneling industry. A HAC can have an angle between 25 and 90 degrees. The current maximum capacity of a HAC is 5000 tonnes per hour with a lift of 90 meters. The lump size of the materials is critical for a HAC to be successful. The schematic below show the principle of the HAC.
| Advantages | Disadvantages |
| Less installed power compared to trucks | High capital costs |
| Ideal for steep open pit mines | Final pit wall is required |
| Less labor intensive than conventional truck haulage | Space requirements |
| Less gas emissions than conventional truck haulage | Capacity up to 5000 tonnes/h |
| Less road maintenance | A max lump size of 250 mm |
| Less dust, noise, and water usage | |
| Successful in the tunneling industry | |
| Easy maintenance due to the use of normal conveyor belts |
3.4 Skip conveying
A skip conveying system has been developed by Thyssenkrupp to transport material more efficiently and with significantly lower environmental impact. It involves an integrated conveying and processing system to avoid heavy truck transportation in deep open pit mines. The schematic representation of the working principle of a skip conveying system is shown below.
The advantages and disadvantages of skip conveying are given below.
| Advantages | Disadvantages |
| Less installed power compared to trucks | High capital costs |
| Ideal for steep open pit mines | Final pit wall is required |
| Less labor intensive than conventional truck haulage | Space requirements |
| Less gas emissions than conventional truck haulage | Only one supplier of the system |
| Less road maintenance | Method has not proven itself yet |
| Less dust, noise, and water usage | Insufficient amount of data available |
| Capacity of 4000 tonnes/h |
3.5 Trucklift system
The Trucklift system is a new development in haulage systems which was developed by Siemag Tecberg. This slope hoisting system accelerates transport from the mine. It can overcome an angle of repose of 50 degrees at 8 m/s. Conventional haulage will require many trucks, which can be reduced by this method. The capacity of this system can reach 4000 tonnes per hour, with a maximum depth of 300 meters. The initial investment is relatively high, but it will decrease the maintenance, spare parts and personnel costs. The schematic below shows the working principle of a Trucklift system.
The advantages and disadvantages of a Trucklift system are given below.
| Advantages | Disadvantages |
| Less installed power compared to trucks | High capital costs |
| For slopes up to 55 degrees | Final pit wall is required |
| Less labor intensive than conventional truck haulage | Space requirements |
| Less gas emissions than conventional truck haulage | Only one supplier of the system |
| Less road maintenance | Capacity up to 4000 tonnes/h |
| Less dust, noise, and water usage | |
Your feedback is important to us. If you enjoyed reading this Global Road Technology industry update and found it informative, please let us know by leaving a REVIEW.
