Experimental Study On The Influence Of Different Coupling Coefficient And Hole Spacing On The Fracture Propagation Of Coal Seam Detonation

Deep hole pre-splitting blasting technology can increase coal seam fracture and improve permeability of coal seam.It is one of the technical measures to effectively prevent coal and gas outburst.The charge structure is one of the key factors affecting the effect of deep hole pre-splitting blasting.At the present stage,most scholars have focused on the formation mechanism of charge structure,the effect of blasting to increase the permeability of coal seam in field engineering practice,for the research content of different charge structure.Based on laboratory test and numerical simulation,the influence of different charge coefficient and hole spacing on the propagation of explosive fractures is studied.The best uncoupling coefficient for blasting fracture propagation is obtained and the setting range of the control hole is determined under the condition of the coefficient.It provides a theoretical basis for the technical parameters design of deep hole pre-splitting blasting.In this paper,the initial impact pressure of the explosion on the coal around mass media blast hole and the damage area of the coal body are calculated under the conditions of different coupling charge.Theoretical analysis is made on the expansion range of crushed zone and fracture zone,and the fracture propagation model of blasting hole and control hole under blasting is established,obtained the fracture extension length of control hole and blast hole.To get an ideal similar material proportioning scheme and basing on the results of the test,a simulation experiment is designed.By analyzing the macroscopic fractures formed on the surface and interior of the blasting specimen and the strain at each test point,at the same time,combined with three-dimensional display dynamic analysis software ANSYS/LS-DYNA simulation results of the model under the above experiment conditions,the influence of each experiment condition on the development of coal blasting fractures is further analyzed from two aspects of experiment and numerical simulation.According to the proportioning test,by reasonably adjusting the ratio of each component,materials with expected strength can be obtained by using cement,sand,gypsum,pulverized coal,and water.The strata of the roof and floor(sand,cement,gypsum,mica powder and water)and coal seam(sand,cement,gypsum,mica powder,pulverized coal and water),and the proportioning is:the strata of the roof(6.2:1.2:0.8:0.06:0.9)and the strata of the floor(6.8:1.0:0.5:0.08:0.9),coal seam(3.2:0.4:1.0:0.05:2.0:0.7).Model tests show that:the ratio of blasting cavities to the original aperture is the largest formed by coupling charge under the explosion load.The diameter of the blasting hole is about 10 times that of the original.The fracture formed near the blasting hole is more dense,but the fracture form is short.When the uncoupling coefficient is 1.5,the diameter of the blasting hole is about 6.5 times that of the original,and the formation of the fractures is longer.Under the condition of the uncoupling coefficient of 2.0,the diameter of the blasting hole is about 2.5 times that of the original,and the formation of the fractures is poor.In the three sets of tests,there are fractures throughout the set of four control holes,indicating that the crack is first formed when there is a control hole.The calculation results of the numerical simulation show that under the condition of the uncoupling coefficient of 1.5,the fracture propagation of coal seam is the best.Then it is obtained that under the uncoupling coefficient 1.5,the spacing of the control hole to the blasting hole should be 2.7?3.3m.