Physical Model Experimental Study On Deformation Characteristics Of Soft Coal Seam Under Blasting

To study the deformation characteristics of soft coal seam under blasting,a three-direction constrained physical model blasting experiment system was constructed,and physical model blasting experiments of "roof-so ft coal seam-floor" structure were carried out.A quantitative characterization method for blasting deformation of soft coal seam was put forward.Combined with density nephogram analysis and electrical resistivity tomography method,the influence law of coal seam strength,explosive dosage and explosive gas on the blasting deformation of soft coal seam was studied(1)A three-direction constrained physical model blasting experiment system was constructed,which mainly included loading device,YBD11 mine network parallel electrical instrument,Canon EOS 60D digital camera,self-made cutting ring and et al The blasting experiment of 0.72m*0.72m*0.3m physical model can be realized.(2)A quantitative characterization method for blasting deformation of soft coal seam was put forward.The blasting deformation of soft coal seam was quantitatively evaluated by calculating the blasting crack area Sa,blasting expansion volume Vc and measuring the blasting cavity volume Vb.The blasting deformation evaluation index V,which is considered from the perspective of volume,can be expressed as V=Sah+Vc-Vb(h is the thickness of the coal seam).When V>0,the blasting deformation of the coal seam is in the loose state;On the contrary,the coal seam is in the state of compression.(3)Physical model blasting experiments of "roof-soft coal seam-floor" structure were carried out,and the influence law of coal seam strength(0.145MPa,0.246MPa,0.354MPa,0.450MPa,0.548MPa),explosive dosage(1.2g,1.7g,2.2g,2.7g,3.2g)and explosive gas on the blasting deformation was studied.It is found that when the coal seam strength is lower than 0.25 MPa,the blasting deformation of the coal seam is in the state of compression;when the explosive dosage is 2.2 g,the blasting crack area is the largest,indicating that there is a explosive dosage that can obtain the maximum blasting crack area in the soft coal seam blasting.(4)A method to analyze the blasting deformation of coal seam by using the density change nephogram before and after blasting was put forward.It is found that there is an obvious compaction area in the soft coal seam after blasting,and the proportion of the compaction area in the coal seam is in the range of 23.9%?61.3%.(5)The regional resistivity variation of soft coal seam before and after blasting was inverted and analyzed by ERT.It is found that there are both increasing and decreasing areas of resistivity in the soft coal seam after blasting.Coal resistivity under the squeezing of explosion gas decreased,whereas the coal resistivity affected only by explosion stress wave increased.The resistivity response results of blasting deformation of soft coal seam are basically consistent with the results of density change during the blasting deformation process.Using blasting deformation quantitative characterization,density nephogram analysis,and ERT method,the influence law of coal seam strength,explosive dosage and explosive gas on the blasting deformation of soft coal seam was obtained,and the local compaction phenomenon in the soft coal seam after blasting is discovered.The research results have important guiding significance for the application of blasting technology in coal seam gas control.Figure[150]table[12]reference[101]...