可视化恒容气固耦合试验系统的研发与应用

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

为定量分析地应力、瓦斯压力、动力扰动等因素对预静载环境下含瓦斯煤物理力学性质的影响规律,获取不同加载路径和不同瓦斯压力下煤岩体物理力学参数,研制了可视化恒容气固耦合试验系统,配合伺服压力机,形成了以可视化恒容试验仪为主体的试验系统.通过实现含瓦斯煤耦合加载室容积恒定消除了气压改变对加载过程的干扰和误差,利用系统自带的环向位移测试装置和可视化窗口实现了对试件体应变增量、煤体裂隙发育与劣化规律等特征参数的全程可视化实时监测.开展了预加静载条件下不同强度型煤试件峰后快速卸气压扰动试验,模拟了现场煤层揭露致使瓦斯压力下降情况.试验结果表明:气体卸压时间在0.55s内完成,随着煤体强度的提高,游离瓦斯对煤岩试件的劣化程度随之降低;当峰值强度低于1 MPa时,游离气体将煤体完全剥离,强度在1.5~2.5 MPa时,卸压扰动对试件仅造成裂隙的进一步扩展;煤体扩容增量随强度的变化符合第一象限单调递减幂函数方程.仪器的研发为深入研究气固耦合条件下含瓦斯煤精确加载与可视化监测提供了新的测试手段和技术支撑.

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 constantvolume 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.