Experiment on damage of coal and rock mass around gas extraction boreholes
In order to study the creep instability characteristics of gas extraction boreholes,we use a digital speckle system to observe the damage and creep process of coal and rock cracks around the borehole during the expansion process,and obtain the damage evolution and creep mechanical characteristics of coal and rock mass around the borehole.The damage of coal samples is divided into slow,intermittent and instantaneous damage types.The cracks produced by the damage and failure of three types of coal samples are mainly caused by the strain along the x direction.Among them,the cumulative increase of damage at different development stages leads to different degrees of fracture development,and finally forms different damage types on the surface of coal samples.Under the constant load stress,with the creep time,the deformation capacity and de-formation space of the coal and rock mass are gradually weakened,which reflects the relationship between the compressive and deformation resistance of the coal and rock mass around the hole and the creep time.
gas extractioncoal rock mass around boreholedamage and destructioncreep characteristicsfracture evolution
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