Study On Damage Law Of Coal Rock Crushing By Ice Abrasive Water Jet

As the country with the most serious coal and gas protrusion disaster,China has conducted a lot of research and practice in the prevention of coal and gas protrusion,and in recent years,with the increasing depth of coal mining,the prevention of coal and gas protrusion needs are of increasing urgency.In particular,the safe and efficient extraction of coalbed methane not only increases the supply of clean energy and reduces greenhouse gas emissions,it is also an urgent requirement for preventing coal and gas protrusion disasters and ensuring safe coal mine production.Water jet slotting technology is an effective approach to increase the permeability of coal seams for gas extraction.The indoor experiments have shown that the ice abrasive jet can significantly expand the slotting range compared with pure water jet,and the melting of ice abrasive avoids the defects such as coal quality degradation and plugging and jamming caused by conventional abrasive jet slotting.Addressing this issue,this paper presents a certain degree of research on the application of ice abrasive jets on coal seam slotting.This paper analyzes the potential of ice abrasive jets in coal seam slotting from three perspectives: acceleration and coal breaking mechanism of ice abrasive jets,comparative analysis of three types of jets and rock breaking law of ice abrasive jets,and the results can provide some theoretical support for the application of ice abrasive jets in coal seam slotting.In this paper,a study on the impact of ice abrasive water jets on coal rocks was carried out through a combination of theoretical derivation and numerical simulation,and the main research contents and conclusions are as follows.(1)Based on the previous research,the force analysis of ice abrasive in high-pressure pipeline was carried out,and the acceleration equation of ice abrasive considering ice particle melting was derived,and the relationship between acceleration and time of ice abrasive in high-pressure pipeline was obtained;the velocity equation of ice abrasive in high-pressure pipeline was derived,and the relationship between velocity and time of ice abrasive in high-pressure pipeline was obtained;the water hammer pressure of ice abrasive jet impacting coal rock considering ice particle crushing was derived,and the relationship between water hammer pressure and time of three jets impacting coal rock was obtained;the mathematical model of spherical stress wave propagation inside coal rock was also established.The water hammer pressure calculation equation is derived,and the relationship between the water hammer pressure and time generated by three kinds of jets impacting coal rocks is obtained;at the same time,the mathematical model of spherical stress wave propagation inside coal rocks is established.(2)The comparative numerical simulation analysis of coal breaking performance of three jets was carried out;the macroscopic fragmentation,fine damage,stress range and energy consumption of the three jets impacting coal rock were compared;the best coal breaking performance of conventional abrasive jets,the second best ice abrasive jets and the worst pure water jets were concluded;it was analyzed that ice abrasive jets can avoid the problems caused by the application of conventional abrasive jets in the coal seam cuttings,and the great potential of ice abrasive jets in the application of coal seam cuttings was demonstrated.(3)Numerical simulations of coal rock crushing by ice abrasive jets under different conditions were carried out;the performance of coal rock crushing by jets under various operating parameters was analyzed;it was concluded that the crushing depth of coal rock increased approximately linearly under a single increase of jet velocity,while there was a maximum value of crushing width;it was concluded that the crushing degree of coal rock showed a trend of increasing first and then leveling off in the region under increasing abrasive concentration;it was concluded that the crushing degree of coal rock under perimeter pressure was smaller than that under no perimeter pressure;it was concluded that the crushing degree of coal rock under perimeter pressure needed to increase jet velocity and abrasive concentration to enhance the crushing degree of coal rock.