岩体破碎技术是解决含硬岩夹矸煤层开采难题的重要手段。液态二氧化碳相变致裂技术作为一种非炸药、低扰动的破岩技术，利用二氧化碳相变过程中产生的高压气体实现岩石破碎，近年来在矿业工程领域展现出良好的应用前景。本文通过物理力学实验、理论分析、数值模拟、现场试验相结合的方法，对二氧化碳岩石致裂机理和裂纹扩展规律进行了研究，结合工程背景开展了现场验证。主要取得如下研究成果：

（1）采用岩石力学试验方法，对硬岩夹矸主要岩性的物理力学特性进行了研究。结合矿物组成与微观结构特征分析，夹矸岩石中脆性矿物含量较高，易于形成复杂裂缝网络。并通过孔隙率与分形维数计算，表明其适合进行致裂改造。

（2）基于热力学理论，采用S-W状态方程分析了液态二氧化碳相变过程中热物性参数的演化规律；利用P-R状态方程描述了二氧化碳气体压力释放过程中的特性，明确了其在临界状态附近剧烈的体积膨胀与压力释放特征。采用压缩气体与水蒸气条件下的泄压能量方法计算了二氧化碳致裂岩体所释放的能量。

（3）分析了液态二氧化碳相变致裂高压气体作用于岩体产生的应力波传播规律与裂纹扩展机制。以二氧化碳基本物理特性为基础，结合弹性理论、断裂力学，揭示了二氧化碳相变破岩致裂机理；结果表明，在应力波作用下岩体产生初始裂隙，随后高压气体楔入裂隙产生气楔效应持续驱动裂隙扩展，当应力强度因子大于岩体裂隙的断裂韧度时，裂隙继续扩展，最终形成宏观裂纹，致使岩体破碎，岩体内部依次形成粉碎区、裂隙区和震动区。

（4）运用LS-DYNA显式动力学软件建立了液态二氧化碳相变致裂岩体的数值模型。通过模拟分析致裂孔间距的合理性，发现合理孔距能有效增强裂纹的贯通效果并提高能量的利用效率。针对自由控制孔的设置，模拟研究揭示了自由控制孔对裂纹演化具有导向作用。针对现有布孔方式存在致裂盲区的问题，设计自由控制孔的优化布孔方案，有效改善了裂纹的扩展路径，提高了岩体破碎效率。

（5）通过在综采面典型硬岩夹矸区域进行范围相变致裂试验。通过钻孔窥视与超声波裂隙探测方法确定了致裂作用范围，并对裂纹连通情况进行分析。致裂后硬岩夹矸的截割比能耗显著降低、单刀截割时间缩短，从而提高煤层回采效率。

Rock crushing technology is an important means to solve the mining problem of coal seams containing hard rock and gangue. Liquid carbon dioxide phase change fracturing technology is a non-explosive, low-disturbance rock breaking technology that uses high-pressure gas generated during the phase change of carbon dioxide to achieve rock crushing. In recent years, it has shown good application prospects in the field of mining engineering. This paper studies the carbon dioxide rock fracturing mechanism and crack propagation law through a combination of physical and mechanical experiments, theoretical analysis, numerical simulation, and field tests, and conducts field verification in combination with engineering background. The main research results are as follows:

（1）The physical and mechanical properties of the main lithology of hard rock gangue were studied by rock mechanics test methods. Combined with the analysis of mineral composition and microstructural characteristics, the content of brittle minerals in the gangue rock is high, which is easy to form a complex fracture network. The porosity and fractal dimension calculations show that it is suitable for fracturing transformation.

（2）Based on thermodynamic theory, the S-W state equation was used to analyze the evolution of thermophysical parameters during the phase change of liquid carbon dioxide. The P-R state equation was used to describe the characteristics of carbon dioxide gas pressure release, and its drastic volume expansion and pressure release characteristics near the critical state were clarified. The energy released by carbon dioxide-induced rock fracturing was calculated using the pressure relief energy method under compressed gas and water vapor conditions.

（3）The stress wave propagation law and crack extension mechanism generated by liquid carbon dioxide phase change fracturing high pressure gas acting on rock mass were analyzed. Based on the basic physical properties of carbon dioxide, combined with elastic theory and fracture mechanics, the mechanism of carbon dioxide phase change rock breaking and fracturing was revealed; the results show that under the action of stress waves, initial cracks are generated in the rock mass, and then the high pressure gas wedges into the cracks to produce gas wedge effect to continuously drive the crack expansion. When the stress intensity factor is greater than the fracture toughness of the rock crack, the crack continues to expand and eventually forms macro cracks, causing the rock mass to break, and the crushing zone, fracture zone and vibration zone are formed in the rock mass in turn.

（4）The numerical model of liquid carbon dioxide phase change fractured rock mass was established using LS-DYNA explicit dynamics software. Through simulation analysis of the rationality of the fracture hole spacing, it was found that a reasonable hole spacing can effectively enhance the crack penetration effect and improve the energy utilization efficiency. Regarding the setting of free control holes, the simulation study revealed that the free control holes have a guiding effect on crack evolution. In view of the problem of fracture blind areas in the existing hole layout method, an optimized hole layout scheme for free control holes was designed, which effectively improved the crack propagation path and improved the rock mass crushing efficiency.

（5）A range phase change fracturing test was conducted in a typical hard rock intercalated gangue area of ​​a fully mechanized mining face. The fracturing range was determined by borehole peek and ultrasonic crack detection methods, and the crack connectivity was analyzed. After fracturing, the cutting specific energy consumption of hard rock intercalated gangue was significantly reduced, and the single-knife cutting time was shortened, thereby improving the coal seam recovery efficiency.

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