Experimental Study On The Multiple Effects Of Extraneous Liquid On Coal Seam

In order to study the effects of different solutions,distilled water and 0.05%KO solution,injected into coal seam on coal strength,gas desorption and dust removal effect of working face and nearby roadway.In this paper,the mechanical property parameters of dry samples,saturated or mixed water samples and saturated or mixed KO samples were compared.The gas desorption and diffusion of dry samples,injected or mixed water samples and injected or mixed KO samples also were compared.The dustfall characteristics of coal face and roadway in different coal mines were studied.Through the above research,the following conclusions are drawn:（1）The compressive strength,elastic modulus and tensile strength of saturated water samples and saturated KO samples showed a downward trend with the increase of liquid content of coal samples,while Poisson ratio showed an upward trend with the increase of liquid content.Under the same liquid content,the tensile strength of saturated KO samples was always higher than that of saturated water samples.The compressive strength and elastic modulus of dry,saturated water and KO samples increased with the increase of geological strength index,while Poisson ratio decreased with the increase of geological strength index.The cohesion of pulverized coal increased first and then decreased with the increase of liquid content,and the internal friction angle did not change much with the increase of liquid content.Furthermore,pulverized coal mixed with KO had the strongest cohesion,and distilled water was the weakest,with dried coal having almost no cohesion.The firmness coefficient of the dry sample is the lowest,and the satiated KO samples is the highest,with the satiated water samples being between.（2）Testing the different liquid content of coal sample’s initial velocity of diffusion of coal gas,which is calledΔp,draw a conclusion that dry coal samplesΔp is highest,with the lowest mixed KO coal samples,and mixed water coal samples somewhere in between.At the same time,Δp decrease with the increase of liquid content.The adsorption and desorption of coal samples were studied by the self-made experimental equipment.It was concluded that the adsorption capacity of dry coal samples was the same as that of liquid injection coal samples,and the residual gas percentage of mixed and injected water coal samples was the largest,while that of mixed and injected coal samples of KO solution was significantly reduced,and that of dried coal samples was the lowest.（3）The results of XRD and FS-SEM observation show that the dust in each mine contains primarily organic matter,as well as considerable amounts of minerals.The chemical composition of dust at the working faces is the most complex,while its composition in the air intake and return roadways is relatively simple.Dust particles mostly exist in the form of agglomerations,or small particles adhering to large particles.XRD results show that the particle size of the dust is mostly of a partial normal distribution,and in some cases there is a trough in the fine or coarse particle section;according to the proportion of PM₁₀,the dust composition can be divided into three types:symmetrical,fine-dominated and coarse-dominated.The PM₁₀proportion shows a decreasing trend from air intake roadways to working faces,to return air roadways.By measuring the contact angle between distilled water and dust in combination with XPS and proximate analysis of dust,it was found that the wettability of dust increases with the increase of the oxygen-carbon ratio on its surface,increase of ash content and decrease of fixed carbon content.The wettability also increases with the decrease of particle size.ICP-MS test results show that the content of harmful elements in dust is mostly higher than that in coal,indicating the complexity of the source.The surfactant adopted in this paper can significantly increase the wettability of coal dust and inhibit the generation of dust to the maximum extent.