预测致裂半径是确定液态CO2相变致裂增透瓦斯抽采技术布孔间距的前提，直接影响瓦斯抽采效果。现有预测方法大多基于单因素。为掌握多因素对液态CO2相变致裂半径的影响规律，有效预测布孔间距，采用ANSYS/LS−DYNA数值模拟软件，结合正交试验，开展了煤层液态CO2相变致裂半径预测研究。数值模拟结果表明：影响液态CO2相变致裂半径的因素主次顺序为地应力＞瓦斯压力＞煤体坚固性系数；致裂半径随地应力增大而减小，随瓦斯压力和煤体坚固性系数增大而增大，且呈线性关系。对数值模拟结果进行多元回归分析，建立了基于地应力、瓦斯压力及煤体坚固性系数3组不同因素耦合条件下的液态CO2相变致裂半径预测模型。在煤矿现场进行工业性试验，基于预测模型计算结果设置抽采钻孔，采用压力指标法对瓦斯抽采效果进行测试分析，结果表明：液态CO2相变致裂孔两侧观测孔的瓦斯压力随时间增加呈递减趋势，且抽采初期距致裂孔越远，则压力越大，与理论分析及数值模拟结果一致；液态CO2相变有效致裂范围与预测结果基本相符；观测孔瓦斯抽采体积分数较自然抽采孔提高73.4%，瓦斯抽采效率显著提高。

Predicting cracking radius is a prerequisite for determining the holes spacing of gas extraction technology by liquid CO2 phase transition cracking and permeability improvement, which directly affects the gas extraction effect. Most existing prediction methods are based on single factor analysis. In order to grasp the influence of multiple factors on the radius of liquid CO2 phase transition cracking and effectively predict the spacing between holes, ANSYS/LS-DYNA numerical simulation software is used to carry out the research on predicting the radius of coal seam liquid CO2 phase transition cracking combing with orthogonal experiments. The numerical simulation results indicate that the order of factors affecting the radius of liquid CO2 phase transition cracking is ground stress>gas pressure>coal solidity coefficient. The cracking radius decreases with the increase of stress, and increases with the increase of gas pressure and coal solidity coefficient with a linear relationship. A multiple regression analysis is conducted on the numerical simulation results. A prediction model for the radius of liquid CO2 phase transition cracking is established based on three different coupling conditions of ground stress, gas pressure, and coal solidity coefficient. Industrial experiments are conducted on the coal mine site. Extraction boreholes are set up based on the predicted model calculation results. The pressure index method is used to test and analyze the gas extraction effect. The results show the following points. The gas pressure in the observation holes on both sides of the liquid CO2 phase transition cracking hole shows a decreasing trend with time. The farther away from the cracking hole in the initial stage of extraction, the greater the gas pressure. It is consistent with theoretical analysis and numerical simulation results. The effective cracking range of liquid CO2 phase transition is basically consistent with the predicted results. The gas volume fraction in the observation hole is 73.4% higher than that in the natural extraction hole, and the gas extraction efficiency is significantly improved.