THE CURRENT STATE OF THE STUDY OF GEOMECHANICAL CONDITIONS OF ROCK MASSES WITH AN INCREASE IN THE DEPTH OF OPEN-PIT MINING

ABSTRACT

In this article, the current state of the study of the geomechanical state of rocks with an increase in the depth of open pit mining and the analysis of the influence of various factors on the stability of the sides and ledges of a quarry have been studied and presented.

АННОТАЦИЯ

В данной статье изучено современное состояние изучения геомеханического состояния горных пород с увеличением глубины открытых горных работ и анализ влияния различных факторов на устойчивость бортов и уступов карьера и представлены.

Keywords: Quarry, edge, ledge, deformation, rock, open pit area, stagnation, landslide, stability of open pit edges.

Ключевые слова: Карьер, борт, уступ, деформация, порода, карьер, застой, оползень, устойчивость бортов карьера.

The development of modern quarries is characterized by a significant increase in depth and a transition to the development of deep-seated ores; the depth of open-pit mining has crossed the mark of a thousand meters from the earth's surface (Table 1, Figure 1) [1-13].

Table 1.

Information about the deep quarries of the world

To substantiate the limiting parameters of the sides and ledges of deep pits, it is necessary to conduct a set of studies of the most significant mining-geological and mining-technical factors (Figure 1), which include:

• study of physical and mechanical properties of mixed rocks;
• structural-tectonic studies;
• hydrogeological research;
• numerical simulation of the stress-strain state of a rock mass by the finite element method in a three-dimensional formulation.

In the practice of open pit mining, all factors affecting the stability of open pit walls can be divided into four groups (Figure 1): engineering-geological, hydro-geological, physical-geographical, mining [14, 15 - 19].

Figure 1. Classification of factors affecting the stability of ledges and pit walls

Prediction of deformation processes is possible on the basis of an integrated approach, including the study of the structural-tectonic structure and strength properties of the massif, instrumental observations of the deformation of various sections of the near-edge massif, assessment of the level and direction of tectonic forces, as well as geomechanical calculations of stability [14, 20 - 22].

The performance of mining operations in a quarry in accordance with the design documentation does not always guarantee the absence of deformations of the sides, local sections of the sides and ledges, especially when forming the ultimate contour of the quarry. The reasons for the resulting violations of the stability of the near-edge massif are different depending on the geological, engineering-geological, hydrogeological conditions and parameters of the side in a particular section of the quarry field [14, 20, 21]. Therefore, each mineral deposit is unique from the point of view of geomechanics and requires an individual approach to determining the factors affecting stability and assessing the degree of their influence.

During open-pit mining, various deformations of the sides of quarries and dumps take place in the form of landslides, collapses and landslides, talus and slush, subsidence [11, 23]. As Fisenko G.L. noted in his work: “There is no clear boundary between individual types of deformations. Screes and collapses differ in the relative size of the deforming massifs, and collapses and landslides differ in the rate of deformation, which depends on the slope of the sliding surface and on the nature of the stress state of the rocks along the sliding surface” [21].

Table 2 presents the classification of quarry wall deformations and the conditions for their occurrence [22].

Table 2.

 Classification of quarry wall deformations

According to the results of the study by Galperin A.M. two thirds of the quarries are subjected to deformation processes. At the same time, there is a trend of increasing cases of loss of slope stability with increasing mining depth. When mining to a depth of 100 m, half of the studied quarries are subject to deformations, with the transition to greater depths, the proportion of quarries increases to 80%. The analysis performed at VIOGEM showed that 75% of the deformations occur in sandy-argillaceous deposits and only 25% occur in slopes composed of rocky and semi-rocky fractured rocks [24].

As noted in their works Umarov F.Ya. and Rybin V.V. With an increase in the depth of existing and planned quarries, the issues of ensuring the stability of the sides and ledges turn into problems of great economic importance [25, 26].

The influence of various factors on the stability of the sides and ledges of quarries has been considered in many works of foreign and domestic authors. An invaluable contribution to the development of geomechanics of open pit mining is made by such scientists as: Melnikov N.V., Rzhevsky V.V., Trubetskoy K.N., Fisenko G.L., Shpakov P.S., Popov V.N., Galperin A.M.

When developing deposits by open method, an urgent task is to ensure the safety and efficiency of mining operations. The solution of this problem is possible on the basis of geomechanical studies of the rock mass and mathematical modeling.

Scientists have been dealing with issues of ensuring the stability of the sides and slopes of a quarry for more than a decade. During this time, several main schools with different and related directions in solving the issues of stability of rock masses have been formed.

Fisenko G. L., Kuvaeva N. N., Poklada G. G., Mochalova A. M., Zoteeva V. G., Tsimbarevich P. M., Galustyan E. L., Popova V. N., Halperina A. M. and others are among the scientists involved in ensuring the stability of open pit mining.

Conclusion

In conclusion, it can be said that despite a large number of studies, the problem of ensuring the stability of the quarry board is still relevant today. The reason for the impossibility of defining a single standard approach to solving this problem lies in the combination of various levels of influence of many factors that determine the individual characteristics of each mining area. Such factors include mining-geological and hydrogeological conditions, changes in the internal physical and mechanical properties of the quarry, effects of explosions and earthquakes, stress-strain conditions, etc.

The way out of this situation is the development of methods and recommendations, including the collection of necessary preliminary data, analysis of research results, and mathematical modeling of stability.

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