Experimental And Mechanism Study On Rock Breaking Performance Of Gunpowder Blasting

The blasting technology based on industrial explosives plays an important role in economic construction and national defense and military fields,but its application in special and sensitive environment is limited by the secondary disaster effect caused by blasting,such as dust pollution,vibration damage,flying stone damage,shock wave and noise pollution.In order to improve the applicability of blasting technology,all kinds of non-explosive blasting technology have developed vigorously.Gunpowder is usually used in the launching and throwing of weapons because of its excellent combustion characteristics and large gas production.In a closed space,It can burn rapidly and produce high temperature and high pressure gas,which has the ability to break rocks.It is a promising blasting material.In this paper,in order to explore the blasting characteristics of gunpowder blasting equipment,the blasting rock breaking experiment,blasting vibration test and blasting flying rock observation were carried out with retired propellant as experimental charge,and the blasting rock breaking performance and blasting harmful effect of gunpowder were studied.At the same time,the rock breaking simulation of gunpowder blasting is carried out by numerical calculation,the influence of hole spacing on blasting effect is studied,and the rock breaking mechanism of gunpowder blasting is discussed and analyzed.Finally,the green sandstone blasting experiments with different charge designs were carried out to provide reference for the application of gunpowder blasting equipment in blasting engineering.The main conclusions are as follows :(1)Through the blasting experiment of gunpowder under different blockage conditions,it is found that the blockage has a great influence on the blasting effect,and the effective blockage is the premise of the successful blasting rock breaking.Using the cement mortar block with a diameter of 50 cm and a height of 50 cm,the rock breaking experiment of gunpowder with a dosage of 5 g ～ 25 g was carried out.It was found that the block size distribution of rock breaking by gunpowder blasting did not change significantly with the dosage,and no crushing zone was found around the hole of the test block.(2)According to the numerical simulation results,it is found that the material around the hole wall has cracks due to tensile failure before reaching the maximum pressure of propellant combustion.The cracks continue to expand to penetration under the action of subsequent expansion gas,while there is no crushing zone around the muzzle,and the crack distribution is basically consistent with the experimental results.The numerical simulation of gunpowder blasting under different hole spacing conditions shows that when the hole spacing is less than or equal to 11 times the diameter of the hole,a straight through crack can be formed between the holes.When the hole spacing is further increased,the cracks between the holes are bent or bifurcated,which affects the smoothness of the cutting surface.Finally,by carrying out the cutting experiment of gunpowder blasting stone under different hole spacing,it is found that with the increase of hole spacing,the smoothness of cutting stone gradually deteriorates,which is consistent with the numerical simulation results.(3)Through the experiment of gunpowder blasting vibration,the attenuation law of gunpowder blasting vibration is obtained.Compared with emulsion explosive,it is found that the peak velocity of gunpowder blasting vibration is significantly smaller than that of emulsion explosive under the same conditions.Using HHT to carry out vertical vibration signal spectrum analysis,it is found that the energy of the propellant vibration signal has a tendency to concentrate to 20-40 Hz in the relatively soft propagation medium.High-speed photography was used to record the process of flying rock throwing in gunpowder blasting.It is found that the velocity of flying stone generally increases with the increase of charge,and the velocity of blasting flying rock in gunpowder blasting was 4.77 ～ 7.56 m/s,and the velocity of blasting flying rock in emulsion explosive blasting was 4.53 ～ 12.42 m/s.