井孔瓦斯抽采过程中抽采气流所携带的煤岩颗粒易在采动裂隙内沉积，严重降低了井孔瓦斯抽采流量，掌握裂隙内颗粒沉积特性是提高井孔瓦斯抽采流量的重要基础。开展了含缩径的裂隙内颗粒运移沉积实验，研究了抽采气流影响下颗粒在越过缩径后的颗粒沉积床演化规律，分析了抽采气速和缩径特征参数对采动裂隙缩径后端颗粒沉积规律和抽采局部阻力的影响。结果表明：裂隙缩径后端颗粒沉积床呈现2种演化规律；当颗粒沉积床沿气流方向呈“V”形分布时，颗粒沉积床沉积高度呈现先快速增大后缓慢减小的演化规律；当颗粒沉积床沿气流方向呈“Ʌ”形的颗粒沉积床时，沉积高度呈现先缓慢增大后缓慢减小的演化规律；此外，随着裂隙内颗粒床的发展，裂隙缩径后端的局部阻力变化可分为初期稳定阶段、快速发展阶段和最终稳定阶段；初期稳定阶段演化时间随抽采气速的增大或缩径比减小而缩短；快速发展阶段演化时间随抽采气速的增大或缩径比增大而缩短。

Coal particles carried by the gas extraction flow are easy to be deposited in the mining-induced fracture, which seriously reduces the flow rate of gas extraction. Mastering the deposition characteristics of particles in the fracture is an important basis for improving the flow rate of gas extraction. In this paper, we carried out a particle transport and deposition experiment in the fracture with a shrinkage, and studied the particle deposition bed evolution law after crossing the shrinkage under the influence of the gas extraction flow. In addition, we analyzed the influence of the gas velocity and shrinkage structure parameter on the particle deposition law of the back end of the shrinkage of the fracture and the local resistance of the gas flow. The results show that the granular sedimentary bed at the back end of the fracture shrinkage shows two kinds of evolution patterns. When the particle deposition bed is distributed in a “V” shape along the airflow direction, the deposition height of the granular deposition bed shows an evolution pattern of rapid increase followed by a slow decrease. When the depositional zone is a “Ʌ” shaped deposition along the direction of flow, the depositional height shows an evolutionary pattern of slow increase and then slow decrease. In addition, with the development of the particle bed in the fracture, the local resistance changes at the back end of the fracture shrinkage can be divided into the initial stabilization stage, the rapid development stage and the final stabilization stage. The evolution time of the initial stabilization stage is shortened with the increase of the pumping rate or the decrease of the shrinkage ratio. The evolution time of the rapid development stage is shortened with the increase of the pumping rate or the increase of the shrinkage ratio.