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Impact of the inclination angle of a blade of the geokhod cutting body on the energy intensity of rock destruction

The article presents the dependence of the energy intensity of rock destruction on the inclination angle of blade of geokhod cutting body for the destruction of low hardness rocks. To formulate the research tasks, the main provisions of the geokhod technology for making workings are presented; the features of the new class of mining equipment, geokhod, are given. The research relevance is formulated. To determine the energy intensity of the rocks destruction, the method of calculating the power and geometric parameters of the geokhod blade cutting body was chosen. An algorithm has been developed for calculating the energy intensity of rock destruction, on the basis of which a computer program has been developed for determining the power parameters of the geokhod blade cutting body. In addition, the article presents well-founded forms of face, which appear as a result of destruction with the blade cutting body of the geokhod. To determine the influence of the inclination angle of the geokhod blade cutting body on the energy intensity of destruction, the geometrical parameters of the blade cutting body and the parameters of the mining and technical conditions of the mine working were justified. As a result of the study, it was revealed that the energy intensity of rock destruction with the blade cutting body decreases unevenly as the inclination angle of the blade towards the reverse cone increases.


Introduction
The formation of a cavity in an underground space at shallow depths is a difficult and time-consuming task. Existing mining systems and technologies of mine workings are poorly adapted, and in most cases are not able to solve problems arising during the development of underground space at small depths [1,2,3,4]. One of the promising approaches to the technology of making workings in small depths is the use of geokhod technology. The main device of the developed technology is a new class of equipmentgeokhod. This is a technological apparatus intended for carrying out the excavation of underground workings for various purposes and location in space [4,5,6,7,8]. One of the variants of the geokhod design is presented in figure 1 [9,10,11]. The use of geokhods with drum-type cutting bodies for the destruction of low hardness rocks [12,13] is not effective from the point of view of safety and complexity of the design of the cutting body itself. A more promising constructive solution of the geokhod cutting body for the destruction of low hardness rocks is the use of blade of the earth-moving machine cutting body [11]. One of the constructive solutions for the geokhod blade cutting body with a diaphragm overlapping the working face is shown in figure 2. In the process of developing constructive solutions for devices and elements of the cutting body of a geokhod, it is necessary to take into account the complex movement of the machine towards the working face. Accordingly, when justifying the power parameters of devices and elements of the cutting body of a geokhod, it is necessary to take into account not only the peculiarities of the interaction of geokhod devices with the external environment, but also the interaction of elements among themselves.
To assess the performance of the executive body of the mining machine, the energy intensity of rock destruction is used [14,15,16]. In geokhod technology of cavity formation in underground space, the energy intensity of the destruction of low hardness rocks will be influenced by the geometrical parameters of the geokhod cutting body. Therefore, the research aimed at determining the influence of the geometrical parameters of the geokhod blade cutting body on the energy intensity of the rock destruction is relevant.

Research methodology
From the developed methodology for determining the energy intensity of rock destruction by earthmoving machines (p, MJ/m 3 ) proposed by Yu. A. Vetrov, the energy intensity is determined by the expression where Pblade cutting force, Н; Fmid -slot cross section area, mm 2 .
One of the parameters that affect the energy intensity of destruction is the slot cross section area. The impact of forces of one blade of geokhod cutting body for the destruction of low hardness rocks is presented in figure 3. For one blade of the geokhod cutting body, the cross-sectional area of the slot will be determined by the expression where b -the blade width, m; h -depth of cutting, m; ksidethe depth ratio of the expansion part of the slot; γ -angle of inclination of the expansion part of the slot to the horizon, degree.
The second parameter affecting the energy intensity of rock destruction is the power factor. For the geokhod blade cutting body, the main power parameters will be the projection of the total force of the resistance of the soil to cutting on the axis of rotation of the geokhod Р0 and on the plane perpendicular to the axis of rotation of the geokhod Rcb, as well as the moment of resistance to cutting from this component of Мcb [14, 15, 16 , 17]. The scheme of action of power factors is presented in figure 4. To determine the energy intensity of rock destruction with a blade cutting body of a geokhod, the cutting force P in expression (1) will be equal to the projection of the total soil resistance to cutting on the plane perpendicular to the axis of rotation of the geokhod Rcb. Therefore, expression (1) takes the form = , .
For a geokhod blade cutting body, the total projection of the resistance of the soil to cutting on a plane perpendicular to the axis of rotation is equal to [14][15][16][17][18][19] Rcb = n(Rcb.cv + Rcb.side), where nthe number of blades of the geokhod body; Rcb.cv -projection of the component of the force of soil resistance to cutting, depending on the width of the cut, on the plane perpendicular to the axis of rotation of the geokhod, Н; Rcb.side -projection of the component of the force of soil resistance to cutting, not depending on the width of the cut, on the plane perpendicular to the axis of rotation of the geokhod, Н.
Projection of the component of the force of soil resistance to cutting, depending on the width of the cut, on the plane perpendicular to the axis of rotation of the geokhod [14][15][16][17][18][19] Projection of the component of the force of soil resistance to cutting, not depending on the width of the cut, on the plane perpendicular to the axis of rotation of the geokhod [18][19][20][21][22][23]  ].
(6) Figure 5 shows the scheme of the geokhod blade cutting body, on which its main geometrical parameters are indicated. One of them is the inclination angle of the blade to the plane perpendicular to the axis of rotation of the geokhod -γ, the change of which affects the shape of the face. At γ = 0°, a flat face shape is formed ( figure 6, a), and at γ > 0° a conic face shape appears ( figure 6, b).

Results
To determine the influence of the inclination angle of the blade to the plane perpendicular to the axis of rotation of the geokhod on the energy intensity of rock destruction, we justified the parameters of mining technical conditions of making workings with geokhods, as well as the geometric parameters of the blade cutting body. The values of these parameters are presented in table 1.  The procedure for calculating the geokhod blade cutting body is shown in figure 7. The developed algorithm was applied when designing a computer program for determining the energy intensity of the rock destruction with the geokhod blade cutting body.  -the energy intensity of the rock destruction decreases as a result of the relative increase in the area of the cut; -from the point of view of the energy intensity of the rock destruction with the geokhod blade cutting body, the conic shape of the face is preferable, as shown in figure 6, b.