Ground support with mechanized shotcreting abbreviates working cycles in underground mining, as it is applied faster than wire mesh. It can be applied in access ramps, caverns and other underground infrastructure, as well as in exploration and extraction galleries.
The main problem of shotcrete logistics in underground mining is the preparation and transport of the concrete mix: How do materials get to the concrete plant, and how is the shotcrete mix transported to the working front?
Depending on the characteristics of the mine (depth, expansion, extraction method, type of ore body, rock conditions), there are different options: install the concrete plant at the surface or underground, and transport the materials via ramps, shaft, a pipe system or a combination of them.
When the concrete plant is at the surface
The installation of the concrete plant at the surface requires a minor investment and is easier and faster than underground. Materials supply is easy, and the plant can be moved if necessary.
Transport of the concrete mix from the surface
The most critical factor is the transport distance. In order to cover large distances, additives are required to stabilize the shotcrete mix. Besides, the larger the distance, the more truck mixers are needed to keep up with the spraying output.
Therefore, the transport distance has a great impact on the cost of the shotcrete mix, equipment operating and maintenance costs. Besides, the higher number of required truck mixers leads to an increase of vehicle traffic in the accesses of the mine, which can hinder the evacuation of the extracted material.
Transport via pipe system
Another option is to transport the shotcrete mixture through a pipe system, which, however, requires more investment and planning. It is necessary to assign a person exclusively for the coordination of material reception and consignment underground, as well as a flawless communication with the surface.
The main advantage is the mine accesses being cleared from additional vehicle traffic due to the reduction of necessary transport equipment. As the truck mixers travel shorter distances, the related operating costs are lower.
In order to transport the shotcrete via pipes, additives need to be used so that the mix does not disaggregate, otherwise it has to be homogenized again underground by means of a remixer or truck mixer.
When the concrete plant is underground
The installation of the concrete plant underground supposes a higher initial investment and is more complicated than it is at the surface, mainly due to the excavation of the required underground cavern.
It is cost-efficient for a certain mine depth or extension, when the transport costs from the surface are superior due to the distances to be travelled.
Transport of the shotcrete materials
Transport by trucks
As the volume of the material to be transported is higher, more trucks are needed, so that the traffic in the mine accesses increases even more.
Transport via pipe system
This option implies the same advantages and disadvantages as in the case of using pipes for the wet mix from the surface plant.