为增加煤层透气性，强化瓦斯抽采效果，提高瓦斯的利用率，提出低渗透煤层液态CO₂气爆致裂增透技术。基于煤矿瓦斯相关基础数据和液态CO₂爆破致裂增透机理，阐述液态CO₂爆破的原理、过程和能量的转化，分析液态CO₂气爆能量释放的TNT当量转化；根据监测爆破过程中致裂器内CO₂压力变化过程曲线的变化情况，分析爆破过程中在致裂器内液态CO2压力在4个不同阶段的变化。采用ANSYS/LS-DYNA模拟软件建立不同爆破参数下的爆破模型，模拟出单孔和双孔液态CO₂爆破演化过程，从Mises应力云图、煤岩损伤云图对比分析液态CO₂爆破效果。利用LS-DYNA有限元分析模拟软件对致裂器不同布置方式下煤岩损伤扩展规律进行模拟。根据数值模拟结果进行CO₂相变爆破工业试验，综合评价液态CO₂气爆致裂增透效果。结果表明：利用相对压力指标法测得单孔爆破半径约2.5 m，与数值模拟结果接近。经CO₂相变爆破后，煤层透气性系数比增透前提高了50多倍；瓦斯抽采体积分数比增透前提高了73.7%；抽采流量是普通抽采孔的5.1倍。数值模拟和现场井下工业试验结果均证明，采用液态CO₂爆破能够提高煤体吸附瓦斯的解吸率，增加低渗透高瓦斯煤层的透气性，促进煤岩体内原生缝隙的发育，使煤层瓦斯抽采效果明显提高。研究成果可为液态CO2气爆工艺的实际施工提供理论依据，为我国低透气性煤层瓦斯抽采难题提供解决办法。

In order to increase the permeability of coal seam, improve the utilization rate of gas and strengthen the effect of gas extraction, the anti-reflection technology of liquid CO₂ gas explosion in low permeability coal seam was put forward. Based on the relevant basic data of coal mine gas and the mechanism of liquid CO₂ blasting cracking and anti-reflection, the principle, process and energy conversion of liquid CO₂ blasting were explained and the TNT equivalent conversion of liquid CO₂ gas explosion energy release was analyzed. According to the change of CO₂ pressure curve in the splitter during the monitoring of blasting, the change of liquid CO₂ pressure in the splitter in four different stages during blasting was analyzed. The coal and rock gas explosion damage model was established by ANSYS/LS-DYNA simulation software. The evolution process of single hole and double hole liquid CO₂ blasting was simulated. The effect of liquid CO₂ blasting was compared and analyzed from the Mises stress cloud map and the coal rock damage cloud map. The LS-DYNA finite element analysis and simulation software was used to simulate the damage propagation law of coal rock under different arrangement of the crack generator. According to the numerical simulation results, industrial tests of CO₂ phase change blasting were carried out to comprehensively evaluate the anti-reflection effect of liquid CO₂ gas explosion cracking and anti-reflection. The results show that the radius of single hole blasting measured by the relative pressure index method is 2.5 m, which is close to the numerical simulation results. After the CO₂ phase change blasting, the permeability coefficient of coal seam is increased by more than 50 times higher than that before the enhancement.The gas extraction concentration was increased by 73.7% compared with that before anti-reflection improvement.The extraction flow rate is 5.1 times that of the normal drainage hole. Numerical simulation and field underground industrial test show that liquid CO₂ blasting can increase the desorption rate of coal adsorbed gas, promote the development of fractures in coal body, achieve the purpose of increasing the permeability of coal seam, and improve the gas extraction effect of coal seam obviously. The research results can provide a theoretical basis for the actual construction of liquid CO₂ gas explosion technology and provide a solution to the problem of gas extraction in low permeability coal seams in China. 

0 引言

1 液态CO₂相变爆破增透技术分析

   1.1 液态CO₂相变爆破器内的压力变化过程

   1.2 液态CO₂爆破器的TNT当量

2 液态CO₂气爆致裂数值模拟分析

   2.1 数值模型的建立

   2.2 钻孔布置参数对爆破致裂效果影响分析

3 二氧化碳增透技术工业试验

   3.1 试验地点概况

   3.2 煤层瓦斯抽采影响半径分析试验

   3.3 液态CO₂现场爆破增透试验钻孔参数设计

   3.4 煤层透气性系数

   3.5 瓦斯抽采效果分析

5 结论