Abstract
Coal seam water injection is an important technical method to prevent and control coal and gas outburst and other disasters. Water can soften coal and change its mechanical properties. In order to study the mechanical properties of coal samples with different moisture content, briquette coal samples with five moistures content (4%, 6%, 8%, 10%, and 12%) were selected to carry out triaxial compression tests under different confining pressures (0.1, 0.2, 0.4, 0.8, and 1.2 MPa). Then, the mechanical response mechanism of the water-bearing briquette coal was analyzed. The results show that the slope of the linear elastic stage of the stress-strain curve gradually decreases with the increase of moisture content. Water-bearing coal exhibits strain strengthening characteristics under high confining pressure, which transforms the water-bearing coal from brittle to ductile state. The peak stress under different moisture content conditions shows a linear relationship with the confining pressure. The internal friction angle decreases linearly with the increase of moisture content. The cohesion varies parabolically with the increase of moisture content and reaches the maximum value when the moisture content is 8%. The coal body with moisture content between 7% and 9% has a high bonding force, which is beneficial to the consolidation of the coal body. Therefore, ensuring a reasonable moisture content of coal through coal seam injection can provide a basis for preventing coal and gas outburst.
Highlights
Coal and gas outburst and rock burst are relatively serious disasters in coal mines, which causes significant property losses and casualties [1,2,3,4,5]
The main purpose of this paper is to study the mechanical properties of briquette coal samples with different moisture content
In the case of fixed confining pressure, with the increase of moisture content, the slope of linear elastic stage decreases as a whole, and the bearing deformation limit increases
Summary
Coal and gas outburst and rock burst are relatively serious disasters in coal mines, which causes significant property losses and casualties [1,2,3,4,5]. It is of great significance to study the influence of different moisture content on the mechanical properties of coal. Many scientists have carried out experiments on the mechanical properties of coal samples with different moisture content [13,14,15,16,17,18,19]. The reason why coal seam with high moisture content can effectively prevent coal and gas outburst is that coal has a stronger adsorption capacity for water molecules than methane molecules [20,21,22]. Some scholars had pointed out that the intensity of coal and gas outburst decreases with the increase of original moisture content [24].
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