EXPERIMENTAL STUDY ON PERMEABILITY CHARACTERISTICS OF COAL SAMPLES UNDER DIFFERENT CONFINING PRESSURES DURING THE WHOLE STRESS-STRAIN PROCESS

摘要

In the course of coal extracting, surrounding rock mass around coal face and roadway is fractured or deformed. The original permeability state of surrounding rock mass also changes, and the new uneven and anisotropy permeability filed is formed. Researches on permeability characteristics with the compression failure process of coal samples is of very great significance for evaluating hydrogeology condition of roof & floor during the extraction and for controlling of surrounding rock water irruption around mining area. In this paper,the permeability tests of coal samples under different confining pressure are carried out on MTS815. 03 electro-hydraulic servo-controlled rock mechanical test system. The results show that the permeability rate curve and the whole stress-strain curve of coal almost have the same development trend. But the permeability rate-strain curve is relatively "hysteretic"which indicates that the close relativity between the evolvement of damage and the development of permeability rate and the permeability developing needs a time course. The permeability of coal presents the tendency of sharply falling on the whole while the effective confining pressure increasing. It shows that the rupture and development of cracks in coal are restricted by the confining pressure.