Abstract
Deep coal cutting is a hot research topic at present. In this paper, the cutting technology of three-drum shearer was proposed based on previous studies. Besides, the influence of confining pressure on coal cutting performance was studied by using the discrete element method, and the induction effect of central cutting on coal cutting performance was discussed. Moreover, coal cutting with different boundary conditions was simulated with the aid of PFC2D software. The results show that as the confining pressure increases, the model dominated by tensile failure does not change, but the crack gradually develops from the vertical direction to the free surface of coal. The cutting debris first increases and then decreases; so does the cutting force. Under the effect of central cutting, the crack tends to develop towards the free surface of coal more, and both the peak cutting force and the specific energy consumption increase with the increase of confining pressure. Induced by central cutting, with the increase of confining pressure, the reduction value of peak cutting force increases first and then decreases while the reduction value of cutting specific energy consumption increases.
Highlights
Coal is the main energy source in China
The three-drum shearer consists of three cutting units, namely, the front cutting unit, the intermediate cutting unit and the rear cutting unit
The cutting fragmentation patterns under different confining pressures are exhibited in figure 10, where the cutting debris is displayed in different colours and the micro-cracks are displayed in the form of line segments
Summary
Coal is the main energy source in China. The coal resource buried within 2000 m is up to 5.9 × 1012 t, of which more than 50% is buried deeper than 1000 m. Li et al [18] obtained the same conclusion This phenomenon may result from the higher thrust forces required for cutting deep rock under higher confining stresses. Field observations indicate that the front abutment pressure existing in front of the mining face may cause rock damage and further improve the cuttability of rock [19,20,21]. In order to improve the cutting performance of coal in front of working face with a depth of over 1000 m, this paper proposed an induced-cutting mining process in the middle of the coal seam based on the threedrum shearer from the perspective of relieving geostress. The differences in coal cutting mechanisms under confining pressure, central cutting and free boundary condition were analysed, and the variation of cutting force and cutting energy consumption under three boundary conditions were discussed. The effect of central mining on rock fragmentation and rock cutting was quantitatively analysed
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