| With the rapid development of society,mineral resources have become the backbone of China's economic development and industrial raw materials production.The main means of exploitation and utilization of mineral resources is blasting.The level of blasting technology not only determines the mining efficiency,safety and cost of mineral resources,but also has a very important influence on the follow-up,transportation and processing of the subsequent mineral resources.The exploitation of limestone by liquid carbon dioxide blasting can not only solve the potential danger and difficulty of the traditional blasting in the limestone mining,but also have high block rate,a significant reduction in the ratio of ore powder,and greatly improved the mining efficiency of limestone.Therefore,it is very important to study this technique for the mining of limestone mine.Firstly,the thermodynamic changes of carbon dioxide during the blasting process are studied.From the macro and micro point of view,the energy transformation of liquid carbon dioxide during the blasting process is analyzed,and the calculation method of the latent heat and expansion work of the gasification is obtained,and the working process of the liquid carbon dioxide blasting technique in the limestone mine is used.And the steps are introduced,and the specific advantages of the liquid carbon dioxide blasting technology are pointed out.By discussing the calculation method of three kinds of physical explosion energy,the calculation method for the energy of the explosive in the explosion process of the liquid carbon dioxide can be determined by the explosive as the compressed gas and the steam explosion energy,and the conversion of the TNT equivalent formula is given.Secondly,the rock breaking process of the combined action of high energy shock wave and low temperature and high pressure carbon dioxide gas produced in the process of liquid carbon dioxide blasting is analyzed,and the rock breaking mechanism of liquid carbon dioxide blasting is summed up,and the thickness of the crushing zone and fracture zone under the action of shock wave and stress wave is derived in combination with the damage theory.The formula of theoretical calculation.The expression of stress intensity factor and effective stress intensity factor of crack tip under the action of primary rock stress and high pressure carbon dioxide gas is derived by introducing the damage theory.According to the theory of linear elasticity,the stress field of crack tip and inside of rock under the action of high pressure carbon dioxide gas is obtained,and the maximum circumferential direction is adopted.Based on normal stress theory,the crack criterion of rock under high pressure carbon dioxide gas driving is derived,and the expression of cracking angle is obtained.Finally,using ANSYS/LS-DYNA software to solve the display,Wang Guan Ying limestone mine as the engineering background,on the basis of blasting parameters,according to the equivalent TNT equivalent are built for single hole and double hole blasting model;combined blasting theory and simulation results,a detailed analysis of the changes of the stress field in the process of blasting,blasting and draw pipe model MZL250-51/1000,ultra deep 0.2m,the effect of blasting hole spacing is 2.5m the best.The ALE algorithm is applied to simulate the damage and cracking process of limestone in single hole and double hole blasting process,and the rule of crack propagation in Limestone during blasting is obtained. |
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