Abstract: The abrupt change area of coal seam dip is one of the complex geological conditions that significantly increase the risk of coal and gas outburst during deep mining. Using a mine in Pingdingshan, Henan Province, as the research subject, we conducted experimental research to simulate coal and gas outburst under various inclination mutation conditions. An interface with a dip mutation was established, positioning raw coal on the upper side and type coal on the lower side to emulate primary and tectonic coal seams, respectively. The initial angle( θ_I) of abrupt change in coal seam dip, the abrupt change angle( θ_M), the critical value of the abrupt change angle( θ_I ), and the gas concentration coefficient(I_θ  ) in the abrupt change area of coal seam dip were defined. The above parameters were used to analyze the effect of abrupt change in coal seam dip on the intensity of coal and gas outburst. The unit outburst intensity(I_U ) was introduced to characterize the strength of coal and gas outburst during the test. Acoustic emission technology was employed to monitor the energy evolution pattern during coal and gas outburst, while temperature changes in each area were recorded using sensors embedded in the sample. The findings of the study indicate that: (1) The abrupt change area of coal seam dip significantly impacts on both the critical gas pressure and the unit outburst intensity during coal and gas outburst. There exists a critical value(θ_T ) of the abrupt change angle in coal seam within the range of 10º<θ_I  ≤20º, 10º≤ θ_M ≤20º. When both θ_I and θ_M  exceed or are equal to θ_T   , a low-index coal and gas outburst becomes more likely to occur. When θ_I  orθ_M is fixed, the unit outburst intensity in the abrupt change area of coal seam dip increases as the gas concentration coefficient( I_θ) increases. (2) A negative correlation exists between θ_I  and both the peak and cumulative AE energy. A similar negative correlation exists between θ_M and both the peak and cumulative AE energy. As bothθ_I  andθ_M  increase, the energy required for the coal body to reach rupture and destabilization progressively diminishes. Under identical geostress conditions, this phenomenon facilitates coal and gas outburst even at lower gas pressures. (3) Notable temperature variations occur within the coal body during the incubation and excitation phases of coal and gas outbursts. Temperature changes in the abrupt change area of coal seam dip are significantly higher than in other zones. Temperature fluctuations in the proximal region of the outburst vent show greater instability than in other regions.

Key words: abrupt change in coal seam dip, coal and gas outburst, unit outburst intensity, acoustic emission energy, temperature