The Influencing Factors And Parameter Optimization Of Carbon Dioxide Blasting In Open-pit Mining

The liquid CO₂ phase change explosion technology utilizes the expansion of the"liquid gas"phase change volume to perform external work,which is a physical explosion.Compared to the chemical explosion of explosives,it has less damage and lower risk,and has unique advantages in both safety and environmental protection.At first,it was only applied to coal mining faces in high gas mines.Later,its application scope expanded from coal mining to non coal mining areas,and its effectiveness was widely recognized.However,there are still many aspects that need further research.This article calculates the explosive equivalent of liquid CO₂ phase change explosion,and explores the blasting characteristics and initiation mechanism through numerical simulation and on-site experiments.The liquid CO₂ phase change explosion pressure test device and test system in the cracking tube were developed and designed,and a series of experimental research and Test effort were carried out.Research on the parameters of CO₂ phase change explosion hole layout and conduct vibration analysis in combination with on-site experiments.The main conclusions are as follows:（1）The energy calculation during the CO₂ phase change explosion process adopts the compressed gas and water vapor container explosion model calculation method,and the emulsion explosive equivalent of the 108#crack tube root crack tube is 2.22kg.The effect of liquid carbon dioxide blasting is significantly different from traditional explosive blasting,exhibiting the characteristics of physical blasting.The rock breaking ability is significantly weaker than that of explosive blasting,and the rock is mostly subjected to tensile damage after blasting.The established three-dimensional double hole numerical model can effectively simulate the effect of liquid carbon dioxide blasting.（2）The independently developed and designed testing device consists of a cracking tube,filling system,accessories,and support frame.The testing system consists of a CY-YD-214pressure sensor,a YE5853 charge signal amplifier,and an HDO4034A oscilloscope.Four small holes are opened on the wall of the cracking tube under high pressure,which can meet the requirements of sealing and pressure resistance.Pressure sensors have the characteristics of wide frequency response,high stiffness,and high pressure resistance,and can be used repeatedly.The testing system has the advantages of fast response,low noise,wide frequency band,high measurement accuracy,and large data processing ability.It not only fully meets the testing requirements of liquid CO₂ phase change explosion pressure,but also has superior performance,providing effective testing and experimental means for accurately testing the phase change explosion pressure inside the cracking tube.（3）The effects and laws of the filling amount of liquid CO₂,the mass of the excitation tube,and the thickness of the constant pressure shear plate were revealed.It was proposed that,under the premise of a certain mass（heat）of the excitation tube and the material and thickness of the constant pressure shear plate,increasing the filling amount of liquid CO₂only increases the amount of the working medium,but does not significantly increase the explosion pressure.Increasing the mass of the excitation agent to a certain value can not only appropriately increase the explosion pressure,Moreover,the peak pressure value and duration of positive pressure are relatively stable,and the thickness of the shear plate increases.The peak pressure of phase change explosion increases more significantly.There is a certain pressure difference in the peak pressure at different positions within the cracking tube,but the difference is not significant.Under the conditions of this experiment,when the thickness of the shear plate is 3.0 mm,the peak pressure is basically around 200.00MPa.When the thickness of the shear plate is 3.5 mm,the peak pressure exceeds 200.00MPa;When the thickness of the shear plate is 4.0 mm,the peak pressure is around 300.00MPa,reaching a maximum of 354.00MPa.（4）Calculate the theoretical and empirical formulas for the spacing between carbon dioxide boreholes,as well as the formula for calculating the spacing between rows.The use of HHT method to analyze the blasting vibration signals generated during blasting construction is a reasonable and effective method,which has great guiding significance for construction.The particle vibration speed of carbon dioxide blasting is much lower than that of traditional explosives blasting,and the vibration energy of carbon dioxide blasting is mainly distributed in the frequency range of 0-100Hz,with a main frequency range of 0-60Hz.The carbon dioxide blasting vibration is within the allowable range and will not have any impact on the engineering construction and surrounding buildings.