Research of land-saving schemes of mining the horizontal sedimentary mineral deposits

Technological mining transport schemes of open development of horizontal sedimentary deposits are considered. Various land-saving technological schemes for transportation of minerals in the absence of a capital trench have been developed. The dependence of the mineral transportation cost on the production capacity of the mine for the developed schemes was established. The research has been carried out for conditions of surface mining manganese deposits of Nikopol Basin. Transport schemes using mobile steeply inclined conveyor are offered. The developed technological solutions for the conditions of surface mining of deposits of the Nikopol manganese ore basin allow not only to reduce the amount of disturbed land, but also to reduce the cost of minerals by reducing its transportation distance by 2 km. The proposed transport schemes will make it possible to obtain an economic effect in the amount of 1–3 million UAH.

An alternative to carrying out a capital trench can be the transportation of minerals to the surface by a steeply inclined conveyor on movable supports [25][26][27][28].However, such a decision requires a technical and economic comparison of existing schemes and promising ones with the use of a mobile steeply inclined conveyor [29][30][31][32].In this regard, the purpose of the study is to substantiate the conditions of use of mobile steeply inclined conveyors for the conditions of development of sedimentary deposits of horizontal occurrence comparing different mining transport schemes.

Methods
The research was carried out by means of technical and economic comparison [33][34][35][36] of several technological mining transport schemes for different production capacity of mine.
For the purposes of techno-economic comparison of technological schemes, three main options for transporting minerals to the surface have been highlighted (Figs.1-3).When calculating their 1319 (2024) 012012 IOP Publishing doi:10.1088/1755-1315/1319/1/012012 2 economic efficiency, the costs of excavation, transportation and loading of minerals in railway transport by cost items: depreciation of fixed assets, costs of materials, electricity, wages and social insurance have been considered.The number of equipment has been calculated in connection with the mine capacity up to 3 million m 3 per year.The same mining equipment of similar parameters was not taken into account.

Results and discussion
Technological mining transport schemes were considered for the conditions of surface mining the manganese deposits of the Nikopol Basin.The ore layer is represented by manganese concretionary inclusions in layers of sand and clay, the average thickness of which is 1.9 m [37][38][39][40].The average thickness of the overburden is 55.7 m [41][42][43][44].Surface mining is carried out according to a combined system with three ledges with parallel movement of the mining front north and formation in the produced space of an internal dump [45][46][47][48].Mineral deposit is connected with the surface through the capital trench in which railway transport is started, which delivers ore to the beneficiation factory at a distance of 10-20 km [49][50][51].In this case, the distance of transporting ore by dump truck is 3 km [52,53].
A typical mining transport system for the development of horizontal deposits involves mining operations with a single-bucket excavator loading the dump trucks, with which the mineral is delivered to the surface using a system of capital trenches.The lower overburden ledge, composed, as a rule, of limestone, is developed by a dragline with placement of the rock mass in the internal dump.The upper ledge, composed of clays, is worked with a rotary excavator in a complex with a dump bridge or a cantilever dump generator with placement of overburden in the internal dump.The forward ledge, usually composed of sands and loams, is developed by a continuous-action excavator in a complex with a main conveyor and a dumper with overburden storage also in an internal dump.Removing the layer of fertile soil is carried out by wheeled scrapers with its placement on the surface of the internal dump after preliminary planning.This system of development allows to reduce the intensity of disturbance of the natural structure of land area.
At the same time, the need for transport communication between the surface and the opening in the mine creates a need for a system of capital trenches, the area of which reaches 200-250 hectares after the mine field is fully developed, In this regard, it is proposed to mine the horizontal deposits using a system of internal temporary capital tranches within the mine field, stockpiling overburden within the mining right-of-way.Further, mining of the deposit should be carried out with the filling of the internal space along the entire width of the mine field.Temporary half-trenches with a width of 5-6 m should be built for access to the equipment on the opening ledges at the ends of the pit, and the transport connection of the surface with the hole should be ensured by constructing an inclined or steeply inclined conveyor on movable supports at the end of the pit.Such a development system will allow to increase the efficiency of reclamation works, as well as not only to preserve the natural structure of land area, but also to restore the natural occurrence and flow of underground aquifers.
According to the first option (scheme 1), the mineral is extracted by the EKH-5A excavator and loaded to the Caterpillar 770G dump trucks, which, through temporary trenches built on the working board and a trench at the end, are delivered to the ore stockpile, from where the second excavator EKH-5A ore is loaded to the railway transport, which transports the mineral for further processing (Fig. 1).
The disadvantages of this scheme are the long distance of transportation of minerals (3 km), an extensive fleet of dump trucks to support the design production capacity, as well as the presence of temporary trenches on the working side of the mine, which complicates the technological process of mining.It should also be noted the clogging the mineral with overburden in connection with its transportation by gravity along the slope of the escarpment, which consists of clays and limestones.To eliminate these shortcomings, a new mining transport scheme using a steeply inclined conveyor is proposed (scheme 2).It consists in the fact that, after extraction by the EKH-5A 1 excavator, the mineral is transported by dump trucks Caterpillar 770G to the steeply inclined conveyor, through which it is fed through the hopper-feeder to the stacker, which places the mineral in the ore stockpile, with the excavator EKH-5A then the mineral is loaded into the railway transport which delivers the mineral to the beneficiation factory.After working out the mining ledge over the entire width of the mine field with the EKH-5A excavator, the steeply inclined conveyor on movable supports is moved along the railway towards the mined-out space (Fig. 2).
The main advantage of scheme 2 is the possibility of conducting internal dumping along the entire width of the mine field, which contributes to increasing the amount of land suitable for reuse.In addition, there is a possibility of through-passage of railway transport, which will significantly increase its productivity.
The most significant drawback of this scheme though is the high cost of mining and transport works due to the inclusion of additional equipment in the technological schemea steeply inclined conveyor and the stacker.Reducing the cost of transportation of minerals can be achieved by reducing the amount of equipment involved, as well as reducing its metal content and material costs.1excavator EKH-5A; 2 -Caterpillar 770G truck; 3railway transport; 4hopper-feeder; 5stacker; 6ore stockpile; 7steeply inclined conveyor; 8movable supports; 9railway So, for example, recently, front wheel loaders have become more and more common at mining enterprises [54].Their advantages over excavators are maneuverability, mobility and lower cost [55].The low height of the mining ledge of 2 m allows replacing two 170 t EKH-5A excavators, the first for mining, the second for overloading, with one Caterpillar 988 H wheel loader weighing 50 t.In this connection, it is proposed a new scheme that preserves all the advantages of scheme 2 and allows to eliminate its shortcomings.It consists in the fact that the mineral is extracted by a wheel loader, after which it is loaded to dump truck and delivered to the ore stockpile.Transportation of mineral to the ore stockpile is carried out until the railway transport comes.Then wheel loader moves to the ore stockpile and starts to load the mineral into the hopper-feeder, with which the mineral is delivered to the surface on a steeply inclined conveyor and loaded to the railway transport through the hopper-feeder.After working out the mineral with a Caterpillar 988 H wheel loader, a steeply inclined conveyor on movable supports moves along the railway in the direction of the created space (see Fig. 3).
A technical and economic comparison of the existing scheme 1 (see Fig. 1) and the proposed schemes 2 and 3 (see Figs. 2, 3) with a change in the production capacity of the pit 0.5-3 million m 3 /year was carried out.According to the received data, the chart of changes in the cost of transportation of 1m 3 of mineral depending on the production capacity of the mine for schemes 1, 2 and 3 was drawn up (Fig. 4).The graph is a power descending function with a periodic increase in the cost value.The size of the period during which growth occurs is equal to the annual productivity of the dump truck.Such changes are because of reaching a certain production capacity for the extraction of minerals, there is a need to purchase an additional dump truck.As a result, the cost of transportation is increasing.Thus, scheme 1 (0.4 million m 3 /year) has the shortest period during which cost growth occurs, since the productivity of the dump truck in this case is the lowest due to the longest transportation distance (3 km).Schemes 2 and 3 make it possible to reduce the transportation distance of the mineral by 2 km, and therefore the productivity of the dump truck when working with them increases, which is reflected in the chart by a longer period during which the cost of transportation increases (0.5 million m 3 /year).
The analysis of the constructed schedule shows that scheme 3 is the most effective from the point of view of minimizing the cost of transportation of minerals.This is because this scheme is characterized by the lowest metal density, costs for materials and maintenance.This scheme is most effective at low production capacity (up to 2-2.1 million m 3 /year).At the same time, scheme 2 is the least effective due to the increase in metal capacity and maintenance costs of the equipment.At the same time, the reduction of the fleet of dump trucks leads to a decrease in the cost of transportation at a high production capacity.Thus, when the productivity of the mine is more than 1.5 million m 3 /year, the transportation of minerals according to scheme 2 becomes more profitable than according to scheme 1, and when the production capacity of 2.1 million m 3 /year is reached, it is more profitable than according to the scheme 3.

Conclusions
The developed technological solutions for the conditions of surface mining of deposits of the Nikopol manganese ore basin allow not only to reduce the amount of disturbed land, but also to reduce the cost of minerals by reducing its transportation distance by 2 km.The proposed transport schemes can be implemented both at the different stages of the deposit development.They will make it possible to obtain an economic effect in the amount of 1-3 million UAH.It has been established that the scheme using a wheel loader as an extraction equipment andin parta dump truck, is the most effective.The cost of 1 m 3 of ore under this scheme will be UAH 4-22.
The obtained results of the research should be used in the design of quarries and mines that develop horisontal deposits, for example, deposits of Nikopol manganese ore, Motronivskyi deposit, Dnipro lignite basin, as well as some lignite deposits of the Dnipro-Donetsk depression.
Further research should be directed towards the search for new resource-saving technologies for the development of mineral deposits of various types of occurrence using surface mining method.

Figure 4 .
Figure 4.The chart of changes in the cost of mining and transportation of 1 m 3 of mineral dependingon the annual production capacity of the mine working up to: scheme 1red; scheme 2green; scheme 3blue