无机触变浆体隔断采空区漏风特性研究

Fully mechanized sublevel caving technology is widely used in China coal mines, which induces excessive residual coal left in the goaf. Meanwhile, the air leakage in the goaf is much more serious because of the promotion of gas drainage technology which bring about frequent occurrence of coal spontaneous combustion. However, due to the wide area of the spontaneous combustion zone in the goaf and the high temperature dot of the coal spontaneous combustion cannot be accurately positioned, conventional fire-retardant materials often lead to highly engineering cost and it is difficult to achieve the expected outcome when the materials were used in underground firefighting. Accordingly, Phase transformation rule and jelling relaxation characteristics of thixotropic slurry will be studied based on thixotropic slurry physicochemical properties analysis, physical simulation experiment and CFD numerical simulation. Experiment study of thixotropic slurry obstruct goaf air leakage will be carried out under different air leakage and stress condition to study the kinetic characteristics of the migration, jelling accumulation and air leakage obstruction laws of thixotropic slurry in the coal rock loose porous medium with spatial and temporal evolution, and then thixotropic slurry migration process mathematical model will be established based on Fluent numerical simulation software to study the liquid phase migration and spatial distribution characteristics of jelling accumulation in porous media. Field industrial test will be carried out to verify, feedback and correct the parameter. The research results will provide a new theory and idea for the fire prevention and extinguishing technology in the goaf.

我国煤矿普遍采用综采放顶煤的开采方式导致采空区遗留残煤多，同时随着瓦斯抽放技术的大力推广，导致采空区内漏风严重，遗煤自燃火灾频繁发生。然而由于采空区内自燃带区域广、遗煤自燃高温点无法准确定位，常规防灭火材料在应用于井下防灭火过程中由于针对性差往往导致工程成本过高且难以取得预期的防治效果。基于此本项目拟通过触变性浆体理化特性分析、相似物理模拟实验和CFD数值模拟，研究触变浆体的相变规律和胶凝弛豫特性，在此基础上结合不同漏风和不同应力环境下触变浆体隔断采空区漏风试验，研究其在煤岩松散多孔介质中的运移、胶凝堆积、漏风隔断规律以及随时空演变的动力学特性，进而以Fluent数值模拟软件为平台，建立反映触变浆体运移过程的数学模型，研究多孔介质内液体相运移及胶凝堆积状态的空间分布特征，并通过现场工业性试验进行验证、反馈及参数修正。研究成果将为采空区防灭火技术提供新的理论和思路。

本项目针对采空区非均质多孔介质裂隙特性，研制了由钠基膨润土、硅酸镁锂、水玻璃、粉煤灰、硅酸盐水泥和无机保水剂所组成的无机触变防灭火凝胶。采用旋转流变仪分析该凝胶的流变学特性及其触变性能，构建了无机触变凝胶的Herschel-Bulkley流变学本构方程，并通过三段式结构恢复和粘弹性测试确定最优配比及溶胶-凝胶相变转换特性。通过程序升温、堵漏风和防灭火性能实验，得出无机触变凝胶具有良好的的保水性、胶凝强度及热稳定性。进一步采用X射线衍射、扫描电镜等测试方法，分析其微观结构，确定了无机触变凝胶的胶凝机理。设计构建了采空区相似物理实验平台，分析了随注浆量及注浆时间，封堵区内气体浓度和温度的变化关系。此外，通过在薛虎沟煤矿开展现场工业性试验，通过对采空区内部进行注浆封堵，实现无机触变凝胶堆积堵漏减小工作面两端压差进而减小漏风，抑制采空区内部遗煤自燃。基于以上实验结果，结合多孔介质扩散理论、气体流动耗散模型、漏风场数学模型、凝胶渗流和堆积模型，构建了采空区注浆堵漏数值计算模型，研究了模型的求解方法，实现了采空区内部气体浓度随凝胶堆积堵漏时间计算求解。项目研究成果对采空区遗煤自燃防治及漏风封堵理论具有重要的意义。