Study On The Characteristics Of Coal-rock Destruction By Carbon Dioxide Blasting

CO2 blasting technology is a new technology of cracking and penetration enhancement in coal seam.In the process of transportation,storage and use,it has the advantages of safety,convenience,stability,environmental protection and low cost,compared with some traditional anti penetration cracking technology.In this paper,through field investigation,theoretical analysis and numerical simulation,the cracking process of CO2 blasting is analyzed on the basis of the field investigation of CO2 blasting fracturing coal-rock and related theoretical knowledge.According to the physical blasting characteristics of C02 cracking,the different types of carbon dioxide cracking pipe is calculated by reasonable theoretical calculation method.The equivalent type two mine emulsion explosive is equivalent.According to the existing blasting theory and the failure criterion,the failure conditions of the crushed zone and the fracture zone are determined.The numerical simulation method is used to study the damage range of the different type cracking device corresponding to the explosive blasting,and the numerical model is improved to make the simulation result more.It conforms to the effect of CO2 blasting cracking.First of all,on the basis of summarizing the domestic and foreign research,through the analysis of the physical and chemical properties of the field and CO2,it is concluded that the release energy of CO2 cracking blasting is divided into two stages,one is the energy released through the CO2 phase transition,and the two is the expansion work generated in the process of CO2 gas expansion.The equivalent amount of type two-mine emulsion explosive for different types of cracking devices was obtained by the conversion of explosive equivalent.The amount of the 38,51 and 57 type cracking devices for the two type-mine emulsion explosives was obtained.Secondly,on the basis of the study of rock blasting theory,the crushing zone around the hole of the coal is produced by the stress wave action produced by the CO2 blasting.The fracture zone is the joint action of the stress wave and the CO2 gas expansion.According to the damage fracture mechanism and the failure criterion,the dynamic compressive strength is judged by the dynamic compressive strength of the crushing zone around the blasting hole,and the fracture zone is determined by the dynamic compressive strength.The dynamic compressive strength is 85.56MPa and the dynamic tensile strength is 0.48MPa based on the judgement of dynamic tensile strength.Finally,by establishing the numerical model of pore size of 2.5cm,3cm and 3.5cm,the radius of comminution to coal-rock is 20cm?30cm,which is 8.5?10 times of the radius of blasting hole.The aperture is 2.5cm,the radius of the fracture zone is within the range of 80cm,the aperture is 3cm,the radius of the fracture zone is within the range of 80cm?100cm,the aperture is 3.5 cm,and the radius of fracture zone is within the range of 100cm?13 0cm.By improving the numerical model of the carbon dioxide cracking device,it is found that the radius of the blasting area is 15cm?20cm,which is 6?8 times of the radius of the hole,and the radius of the fracture zone is between 60cm?80cm.The spacing of blasting holes is suggested to be 1.2m.