液氮致裂层理煤体热–流–固–损伤耦合模型及数值模拟研究  

A thermal-hydraulic-mechanical-damage coupling model of layer coal fracturing by liquid nitrogen

作　　者：林海飞 李博涛[1] 李树刚 宋兆雪 王裴[1] 罗荣卫 魏宗勇 秦雷 LIN Haifei;LI Botao;LI Shugang;SONG Zhaoxue;WANG Pei;LUO Rongwei;WEI Zongyong;QIN Lei(College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Key Laboratory of Western Mine Exploitation and Hazard Prevention,Ministry of Education,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Yankuang Energy Group Company Limited,Zoucheng,Shandong 273500,China)

机构地区：[1]西安科技大学安全科学与工程学院,陕西西安710054 [2]西安科技大学西部矿井开采及灾害防治教育部重点实验室,陕西西安710054 [3]兖矿能源集团股份有限公司,山东邹城273500

出　　处：《岩石力学与工程学报》2024年第5期1110-1123,共14页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金面上项目(51874236);陕西省杰出青年科学基金项目(2020JC–48);陕煤联合基金重点培育项目(2019JLP–02)。

摘　　要：煤体原生层理对煤体力学性质有显著影响,为探究液氮低温致裂层理煤体裂纹扩展及劣化失稳机制,基于细观基元理论和损伤力学理论建立热–流–固–损伤耦合模型,并利用COMSOL软件模拟获得不同应力比下液氮致裂层理煤体裂纹扩展分布特征,分析压裂过程中煤体损伤、渗透率和温度的演化规律。结果表明:液氮注入煤体初期(5 s),钻孔附近与液氮接触煤体温度急剧下降形成小范围超低温区,产生的热应力超过煤体抗拉强度,在钻孔周围产生损伤破坏区域。随着液氮注入压力增加,煤体内部出现多条主裂纹,主裂纹主要沿层理方向发育并生成次生裂隙,且钻孔周围形成复杂破坏区域,煤体损伤开始增大,渗透率也随之增加;注入压力持续增加煤体进入失稳阶段,煤样内部大量裂纹贯通,煤体发生破坏,煤体损伤和渗透率也逐渐达到峰值。煤体损伤、裂隙压力与渗透率随着煤体层理角度增加呈增加后减小趋势,层理角度为45°时达到最大值;煤体损伤、裂隙压力与渗透率在应力比为0.5时达到最大,应力比从0.5增大到1时大幅减小,应力比超过1后逐渐趋于平稳。层理对煤体液氮压裂的起裂压力影响显著,不同层理角度条件下煤体液氮压裂起裂压力变化规律相似,随层理角度增加,起裂压力呈现出先减小后增大“U”型变化趋势;相同层理角度下,随着应力比增加起裂压力逐渐增加。研究结果为进一步掌握液氮压裂煤体技术,确定液氮致裂工艺参数提供了依据。The mechanical properties of coal are heavily influenced by the primary bedding fractures.To investigate the crack expansion and destabilization mechanism of liquid nitrogen(LN)low-temperature fractured layer coal 2,a thermal-fluid-solid-damage coupling model was established based on meso-element theory and damage mechanics.The evolution of coal damage,permeability and temperature were analyzed throughout the fracturing process,along with the distribution characteristics of crack propagation in layer coal induced by LN fracturing during various 2 stress ratios,as obtained by COMSOL software simulation.The results indicate that the temperature of the coal in contact with LN near the drill hole drops sharply to form a small range of ul 2 tra-low-temperature zone,which generates thermal stresses exceeding the tensile strength of the coal,and produces damage around the drill hole and destroys the damage area in the initial stage of LN injection(5 s).With the increase of 2 LN injection pressure 2,multiple main cracks appeared inside the coal.The main cracks were mainly developed along layer direction and generated secondary fissures and a complex damage area was formed around the borehole.The number of coal damage begins to increase,accompanied by a corresponding increase in permeability.With a continuous increase in injection pressure,the coal enters an instability stage.A large number of cracks extensively penetrate the coal specimen,leading to coal damage.During this process,both permeability and fracture pressure gradually reach the peak values.The coal damage,fracture pressure,and permeability exhibit a trend of increasing and then decreasing with increasing layer angle,and reach the maximum value when the layer angle is 45°.The coal damage,fracture pressure and permeability reached the maximum when the stress ratio was 0.5,decreased dramatically when the stress ratio increased from 0.5 to 1,and gradually leveled off after the stress ratio exceeded 1.The existence of coal layer has a greater influence on the ini

关 键 词：采矿工程 液氮压裂 层理煤体 热–流–固–损伤耦合 裂纹扩展 起裂压力 

分 类 号：TD32[矿业工程—矿井建设]