Experimental study of the seepage properties of the compacted particle coal under gradual loading

CHU Tingxiang; JIANG Deyi; YU Minggao

Abstract：In order to identify the effects of the vertical tress and the grain size to the permeability of the compacted broken coal,the relations between the permeability and the stress,particle size,seepage pressure gradient were established by the seepage experiment of the compacted broken coal.The results indicated that:1) the stress-strain curves of the compacted coal particles have obvious stage characteristics,which are faster within the range of 0 to 6 MPa and are slower during the range of 6 to 12 MPa,and the compaction is weaker after 12 MPa.2) the permeability generally reduces with increase of the vertical stress,and the absolute value of the non-Darcy coefficient generally increases with increase of the vertical stress,but the non-Darcy coefficient is negative in all tested.3) under the same vertical stress loading,the porosity and the permeability decrease with the increase of the grain diameter,and the attenuation degree of porosity and permeability increases with the increase of the coal grain diameter.4) the physical structure is changed in the process of stress loading,resulting in the change of the graded composition.The fracture fractal dimension increases and the coal particles breaks again,which influences the penetration behaviors.5) By the seepage experiment of the compacted broken coal,we study the stress recovery in gob which could reduce the porosity and the permeability.Reducing the degree of broken and the percentage of small particles are favorable to rcduce the porosity and the permeability,which is advantage to prevent the coal self-heating.