Abstract: In room-pillar and roadway gangue backfill mining, the coal pillar and gangue are interval, and crushed gangue are under confined compression, besides which, the compaction, porosity and seepage properties of crushed gangue play a significant role in the control of coal seam gas and groundwater flow. Based on the steady-state flow measurement and axial displacement control method, a self–designed testing system for water flow in crushed rocks has been used to monitor the non-Darcy seepage properties of mixture particles of crushed gangue under confined water pressure, and the experiment has obtained the relation between seepage properties (permeability k and non-Darcy coefficient β) and porosity. Testing results have indicated that: 1) The Re calculation and the pore pressure gradient and flow velocity curves have shown that the water seepage flow in crushed gangue is a non-Darcy flow. 2) The porosity of crushed gangue is strongly influenced by compaction (axial displacement) and particle mixture. The porosity decreases with the increase of axial displacement and decrease of bigger particle size, respectively. 3) During the compaction, some larger particles being crushed and broken is the main reason that gave birth to particle size of 0-2.5 mm, and small particles have been washed away because of the effect of water seepage. 4) In general, under confined compression, the permeability k decreases while the non-Darcy coefficient β increases. The fluctuation of seepage properties curves has shown that the seepage properties of crushed gangue are not only related to compaction levels, mixture sizes, particle crushing, style of arrangement, but also to the pore channel.

Key words: crushed gangue, confined compression, mixture particles, non-Darcy flow, seepage properties, particle crush