ON THE ISSUE OF COMPREHENSIVE DEVELOPMENT OF THE TUGAN DEPOSIT

V. V. PROSKURYAKOV, S. S. RISHNYAK

(Presented by the Scientific and Technical Conference on the Use of Mineral Resources of the Tomsk Economic Region)

In recent years, a considerable number of deposits have been discovered and partially explored within the territory of Tomsk Oblast, among which the largest and most promising is the Tugan placer deposit.

A characteristic feature of this deposit is the great variety of useful components. The overburden rocks, with the exception of the upper layer of peat bogs and loams, whose thickness averages 2.4 m, consist of high-quality glass, molding, and concrete sands, clays, brown coal, and siliceous sandstones. The productive bed, which is the principal object of development, contains 60–65% pure quartz sand and 5–10% kaolin.

In view of these features, development of the Tugan deposit must be carried out comprehensively, with maximum utilization of the extracted mineral raw material.

The comprehensive development of the deposit is dictated by the following circumstances. Molding and glass sands for the needs of Tomsk plants are currently brought in from Chelyabinsk, Sverdlovsk, Irkutsk, and other oblasts. The selling price of 1 t of sand at the mining site is on average 10 rubles, while the cost of transporting 1 t of sand is 82 rubles. The cost of 1 t of kaolin, as a rubber filler, brought in from the European part of the USSR, is 140–150 rubles.

But the matter is not only the high cost of sand and kaolin and the irrational use of railway transport. The point is that individual economic councils, in connection with the exhaustion of local quarries, have refused to satisfy requests for the supply of sands, thereby placing Tomsk enterprises in a difficult position. At the same time, both the sands and the kaolin of the Tugan deposit are not inferior in quality to imported materials.

For several years the Tomsk Electric-Lamp Plant has been extracting Tugan glass sands for its own needs. The work here was carried out manually, without the use of machines. As a result, the volume of extraction did not exceed 1–2 thousand t per year, and the cost of 1 t of sand was 50 rubles.

Quarries for the extraction of building materials—stone, crushed stone, gravel, etc.—are in the same situation. The main shortcoming of the quarry sector in the region is the departmental fragmentation of the quarries, as a result of which almost all of them are of a dwarf character, are poorly mechanized, have low labor productivity, and yield extracted sands at high cost.

In the coming seven-year period the volume of capital construction will increase sharply; in this connection the demand for building materials will grow considerably. Meanwhile, the comprehensively mechanized development of the Tugan deposit will fully satisfy the needs of enterprises of Tomsk Oblast for kaolin, glass sands, molding sands, and other building materials, and will also make it possible to supply these materials to neighboring oblasts, in particular to Novosibirsk and Kemerovo, which have a great need for them.

On the basis of the Tugan quarries a complex of industrial enterprises can be built: a mining-and-processing combine, plants for the production of concrete, glass and ceramic products, brick, and prefabricated building structures.

In connection with this it is necessary that operation of the quarry proceed without interruption throughout the entire year. Seasonal work is undesirable, since it will lead to the immobilization for a long period of powerful equipment, to labor turnover, and will sharply complicate the organization of work at the enterprises.

At the same time, under the conditions of the long Siberian winters with low temperatures, excavation of frozen soils presents great difficulties. Practice shows that, for the most part, all existing earth-moving machines are not adapted for direct excavation of frozen soils under winter conditions, even with a slight depth of freezing. The depth of soil freezing in the area of the city of Tomsk reaches 2.1 m and more. This circumstance is aggravated by the need for separate excavation of individual beds and for in-pit selective mining of the useful mineral.

In recent years, separate excavation has begun to be used in developing sequences of closely spaced coal seams, as well as complex deposits of iron ores. In the quarries of nonferrous metallurgy and building materials it has not yet become widespread. This is explained by insufficient study and by the absence of scientifically substantiated methods for the separate working of complex deposits. All this also makes it difficult to choose a rational method for mechanizing mining operations.

In modern open-pit workings, in the production of both extraction and stripping operations, the following types of mechanization have become most widespread: multi-bucket and single-bucket excavators, bulldozers, scrapers, and hydraulic mechanization.

Multi-bucket excavators, especially rotary excavators, when working loose rocks ensure high productivity and good separate excavation of beds. However, these excavators have a substantial shortcoming: they are not adapted to work in rocky and frozen rocks, even when blasting operations are used.

Single-bucket excavators of the mechanical-shovel type work successfully in all kinds of rock. They provide partial separate excavation of beds and isolated extraction of heterogeneous material in complex faces. Therefore, the use of single-bucket excavators (of the EKG-4 type) is at present the most effective form of mechanization of work in the quarry.

At the Tugan quarries, scrapers and bulldozers will play an important role. The experience of foreign quarries, in particular in the United States and England, shows that at many coal strip mines, powerful wheel scrapers compete with excavators in stripping operations, as a result of which they have become widely used there.

Over most of the areas of the Tugan deposit, the width of the quarry fields does not exceed 900 m, and the thickness of the loose overburden rocks averages 2.4 m. Under such conditions, removing waste rock beyond the contour of the quarry by powerful scraper units with tractor traction is the most convenient and economical method.

Hydraulic mining under the conditions of the Tugan deposit, in our opinion, will not find wide application for the following reasons:

a) unreliability of operation in winter;
b) the impossibility of high-quality selective extraction of seams;
c) the difficulty of controlling the movement of pulp where the hypsometry of the seams is complex;
d) a shortage of pressure water and electric power.

In summer, preliminary loosening of the rocks is necessary only when extracting the siliceous sandstone seam, which occurs in the northern part of the deposit. In winter, excavation by excavators of both overburden rocks and sands will require their preliminary loosening by blasting. However, blasting frozen ground presents considerable difficulty.

It has repeatedly been noted in mining-engineering literature that at present there are still no generally accepted recommendations for carrying out blasting operations in frozen ground. Therefore, in connection with the development of open-pit mining in the eastern, and especially in the northern, regions of the country, the search for effective methods of mining frozen ground is becoming important.

In practice, when mining frozen rocks, the methods most often used are loosening them by blasting, preliminary warming, or thawing of the faces. Taking into account the need for selective extraction of seams, when loosening rocks on benches it is advisable to switch to directional drilling of boreholes instead of vertical ones. The transition to directional drilling of boreholes parallel to the footwall of the siliceous sandstone seam will make it possible: a) to use more productive rotary drilling rigs; b) to drill boreholes through soft interbeds without crossing the siliceous sandstone seam; c) to increase drilling productivity by 10–15 times in comparison with the shothole or cable-tool method of drilling boreholes.

Directional boreholes should also be used for loosening frozen rock layers in the roof and on the slopes of benches.

Preliminary warming of faces by means of straw mats, snow retention, and other methods is economically expedient, especially when extracting sands with bucket-wheel excavators, when blasting them hampers the work of the excavators. Calculations show that preliminary warming of faces before the onset of frosts is 4–5 times more economical than subsequent thawing of frozen rocks. This issue must be given due attention.

Quarry transport is an important component of the technological complex of stripping and extraction operations; it has a substantial influence on the technical-and-economic performance indicators of quarry operation. At present, in open-pit workings, the following is used

four principal types of transport: rail, motor-vehicle, conveyor, and hydraulic.

The use of conveyor transport in the development of first-priority areas will be unlikely, owing to the unreliability of its operation under severe climatic conditions. Wet rock will freeze to conveyor belts, since the sands of the Tugan deposit are water-saturated and often contain many clayey fractions; at low temperatures the resilience and elasticity of the belt decrease and it wears out rapidly; it is impossible to transport heterogeneous raw material by conveyor when selective extraction is used; the construction of surface galleries and their heating in winter are required.

The use of hydraulic transport is most probable for transporting sands from the open pit to the concentrating mill. As can be seen from Table 1, the cost of hydraulic transport is approximately 2 times lower than that of motor-vehicle and conveyor transport and 3 times lower than that of rail transport. However, the question of the type of transport for Tugan requires additional studies, first of all with respect to the amount of water and electric power, and also with respect to the reliability of pipelines and mixing installations under winter conditions.

An analysis of the use of motor-vehicle and rail transport shows that the former has the following advantages: a) convenient mining of small open-pit fields with a complex geometry of the areas; b) reduced costs and construction periods, and rapid commissioning of open pits owing to smaller volumes of capital and preparatory work; c) better conditions are created for achieving higher open-pit productivity with a limited work front; d) favorable conditions for applying separate extraction of the mineral by grades.

The disadvantages of motor-vehicle transport include the labor intensity of repairing and servicing motor vehicles.

Table 1 gives technical and economic data for various types of transport of sands to the concentrating mill in the development of the Samotkan deposit, whose mining-geological conditions are approximately analogous to those of the Tugan deposit [1].

Table 1

On the basis of an analysis of technical and economic factors, it is possible to recommend dump trucks with a carrying capacity of 10–25 tons for transporting the sands.

The considered methods of mechanizing the excavation and transport of overburden rocks and the useful mineral make it possible to outline the following schemes for developing the first-priority sections of the Tugan deposit.

The overburden rocks, represented by peat bogs, loams, and partly clays, are removed beyond the limits of the quarry field by wheeled scrapers with a capacity of 6–10 \(m^3\). In view of the small thickness of the cover rocks—on average 2.4 m—the stripping operations are carried out seasonally, in summer.

Foundry and glass sands, occurring in the form of large lenses, are mined in one bench 4–7 m high by an EKG-4 excavator and are hauled to external stockpiles by dump trucks.

The sands are also mined by an EKG-4 excavator, with haulage by dump trucks to the concentrating plant. The latter sands are, to a considerable degree, water-saturated; therefore their excavation in winter may be carried out with the use of drilling-and-blasting operations or with preliminary insulation of the face by means of straw mats 30 cm thick, protecting the bench roof and slope from freezing. According to this scheme, a number of sections of the deposit may be mined.

Table 2 gives the cost indices for excavation and transportation of \(1\ m^3\) of sand for one of the sections, calculated at the Department of Development of Stratified Deposits of the Tomsk Polytechnic Institute.

Table 2

The cost of mining \(1\ m^3\) of sand when excavating it with EKG-4 excavators and transporting it by MAZ-525 dump trucks on the indicated section (not including overhead costs and services of auxiliary shops) amounts, with comprehensive utilization of the deposit, to 3.0 rubles. Without comprehensive utilization, with an average stripping ratio of 1.1, the cost of \(1\ m^3\) of sand will be 4 rubles 70 kopecks.

The development of other sections is complicated by a high stripping ratio (about 4) and by the high water content of the sands. Over a considerable area the bed is overlain by siliceous sandstone 1.3–5.2 m thick. Its excavation will require the use of blasting operations.

Of the productive sands, only the middle part deserves attention. In this connection, it is proposed to work off the upper layer of the bed by a transportless scheme, with the sand being stockpiled on the floor of the quarry.

According to preliminary calculations, the cost of selective mining of \(1\ m^3\) of sand will be 11 rubles 98 kopecks, and, taking account of comprehensive utilization of the deposit, 6 rubles 50 kopecks.

Conclusions

1. Industrial development of the Tugan deposit will be of great importance for the national economy.

2. Development of the deposit must be carried out comprehensively, with maximum utilization of the diverse mineral raw material.

3. For the first-stage areas, it is possible to recommend a transport system of development with separate stockpiling of the sands and removal of overburden beyond the limits of the quarry field by powerful scraper units.

4. In planning research work, it is necessary first of all to carry out: a search for effective methods of developing frozen soils; selection of the type of transport in accordance with the adopted scheme for beneficiation of the sands; and establishment of the main parameters of development systems as applied to local climatic conditions, with orientation toward year-round operation of the quarry.

References

1. Bornsenko M. D. and Shugaev I. A., Development of the Samotkan Deposit by the Open-Pit Method. Mining Journal, No. 3, 1958.