Development and application of a gas-solid coupling test system in the visual and constant volume loading state

LI Qingchuan; WANG Hanpeng; LI Shucai; YUAN Liang; XUE Junhua; CHEN Benliang; REN Bo

Abstract：A gas-solid coupling test system in the visual and constant volume loading state was developed to quantitatively analyze the influence of stress,gas pressure,dynamic disturbance on physical mechanical properties of coal containing gas in static pre-loading conditions,and to acquire the coal physical and mechanics parameters under different loading paths and gas pressure.Combined with the servo press,the experimental system based on the visual and constant volume tester was established.By realizing the constant volume of coupling loading chamber during the loading process of the coal containing gas,disturbance and error influence due to the change in pressure was eliminated.The tester combined with circumferential displacement testing device and visual windows can realize the real-time visualization monitoring of coal volume strain increment,fracture development and degradation law during the whole process.On this basis,through a gas pressure instantaneous releasing test of post-failure coal specimen in the static preloaded conditions,the gas pressure drawdown as a result of coal seam disclosing was simulated.The results show that the gas unloading can be completed in 0.55 s.With the increasing of coal strength,the degradation effect of free gas on coal specimen declines.When the peak strength is less than 1 MPa,the coal is entirely separated by free gas.When it ranges between 1.5 MPa and 2.5 MPa,the gas pressure releasing disturbance only leads to further extension of fractures.The variation of coal volume strain increment with strength follows the monotone decreasing power function equation in the first quadrant.The research and development of the system provides a new method for further study of the accurate loading and the visualization monitoring of coal containing gas.