Experimental Study On Shear Damage Law Of Water-Bearing Coal Samples

The western mining area has gradually become the focus of coal resources development in China,but the lack of water resources has become the bottleneck restricting the development of local coal resources.Therefore,coal and water co extraction is imperative.At present,the coal water co production methods mainly include water preserved mining technology and underground reservoir technology.Especially the underground reservoir has large-scale application in Shendong mining area.The stability of the underground reservoir is closely related to the stability of the artificial dam and the pillar.The failure of the coal pillar dam is not only related to the load,but also affected by the erosion of water.Therefore,the study of shear failure characteristics of coal samples under different water content is great significance to reveal the deformation characteristics of coal pillar-dam under the action of water.In this paper,the main research object is the damage law of shear failure of water bearing coal samples.The shear failure strength and characteristic parameters of coal samples are systematically studied by compression shear test.By means of acoustic emission and infrared radiation,the shear process of coal samples with different moisture content is inversed and analyzed,then we obtain the acoustic emission and infrared radiation characteristics of coal samples under different water cut conditions,and taking this as a model,the damage law of the shear failure process of water bearing coal samples is analyzed.The paper starting with water absorption experiment,we determined 5 soaking time points at first;The shear test shows that the shear strength of the coal sample decreases gradually with the increase of water content,and the relationship between the two decreases exponentially.And the shear strength parameters of c and ψ were analyzed,two coal samples after immersion were decreased,At the same time,based on the moisture content,corrected the Mohr Kulun failure criterion parameters.Through the research on the acoustic emission parameters of shear process,AE counts and energy characteristics and correlation with changes of stress strain curve,namely with the increase of water cut,acoustic emission counts and energy characteristics is not obvious;By analyzing the infrared characteristic parameter AIRT of the shearing process,it is found that the temperature range of AIRT decreases continuously with the increase of water content,and the highest and lowest radiation temperatures exhibit the same trend.Combined with the parameters of surface radiation temperature,entropy and variance,the higher the moisture content,the smaller the variance of the surface temperature;By establishing the integral damage variables based on the acoustic emission counting characteristics and the surface damage variables based on the infrared radiation temperature change point.The overall damage variable shows that the coal sample is more precursory and periodic,while the surface damage variable is more fitted to the stress time curve at the peak failure stage.Finally,the coal shear damage model is evaluated,which provides a reliable basis for the study of the stability of the coal pillar.