煤与瓦斯突出渗透失稳机理研究

According to the standards for classification of rock mass structure, damage degree Ⅲ,Ⅳ and Ⅴ coal seams in "coal and gas outburst prevention provisions",which are called "tectonic coal" in coal geology,were regarded as loose structure rock mass,which are treated as soil in geotechnical engineering.Based on the soil flow theory of soil mechanics,an analysis was conducted on the surface coalfield drilling,the pressurized test of the gateway in lab. A view was provided that the coal gas outburst be the permeability stability lost．An outburst could be divided into three stages．The first stage would be a stage in which coal seams were crashed and gas pressure gradient fields were adjusted by crustal stress. The second stage would be a seam lost stability stage by gas permeation pressure induced by gas pressure gradient.The third stage would be the coal particles migrating stage by the gas expansion power. The gas pressure gradient of the seam would be cinsidered as a strength index that prevents the outburst occuring. The following works would be done: Firstly, a test woud be made to verify whether there be a critical gas pressure gradient when outburst occures. Secondly, another test would be made to determine the relationship between the rate of gas pressure gradient decreasing and the outburst magnitude.Thirdly, a mathematical model on coal seams permeation stability lost would be established, based on the analysis of influence ingredients on critical gas pressure gradient.

按《防治煤与瓦斯突出规定》，"破坏类型为Ⅲ、Ⅳ、Ⅴ类的煤层"是判定煤层是否会发生突出的单项指标之一。此类煤体为粒状、土状，手捻即碎，硬度低，煤地质学称这类煤体为"构造煤"，申请人按照岩体结构分类，将之划归为散体状结构岩体。在岩土工程中，具有散体状结构的岩体通常按土体处理。在分析地面煤田钻井抑突效应和蒋承林巷道增压抑突试验成果的基础上，借鉴土力学流土理论，申请人提出煤与瓦斯突出属渗透失稳的观点。把突出分为在地应力作用下的煤体破碎及瓦斯压力梯度的调整、在渗透压力作用下的煤体失稳和在膨胀能作用下的煤粉搬运3个阶段，认为"构造煤"是渗透失稳的物性基础，渗透失稳是"构造煤"发生失稳的具体模式，煤体抗失稳强度用临界失稳梯度表示。本项目拟研究：①通过试验检验煤层是否存在临界失稳梯度；②通过试验检验加快煤层瓦斯压力梯度下降速率能否降低突出强度；③研究临界失稳梯度的影响因素，建立煤层渗透失稳的数学物理模型。

研究内容包括：①建立煤层一维渗透失稳判别式；②研制煤层一维渗透失稳试验装置；③进行了煤层一维渗透失稳模拟试验，对所建立的煤层一维渗透失稳判别式的合理性进行了验证；④建立煤层一维持续渗透失稳数学模型；⑤研究煤层瓦斯压力梯度下降速率对突出强度影响。.取得的主要成果包括：①以煤地质学“构造煤”理论为基础，借鉴土力学对流土问题的分析方法分析煤与瓦斯突出的渗透失稳机理，初步建立了煤层一维渗透失稳判别式。②研制了渗透失稳模拟试验装置，试验装置包括煤样室、模拟巷道、煤样压实装置、揭煤装置、气压和流量量测系统和注气系统。③进行了煤层渗透失稳模拟试验，对所推导的临界失稳梯度计算公式的合理性进行初步验证。④基于多孔介质流体动力学理论，假设煤壁背景气压呈指数衰减，结合理想气体状态方程、达西定律和已建立的煤层一维渗透失稳判别式，建立煤层一维持续渗透失稳数学模型, 采用有限差分法对方程求解，得到煤层分层渗透失稳的一些规律。⑤提出反滤层控突方法，进行了有、无反滤层揭煤对比试验，结果表明：反滤层的控突效果明显。⑥进行了密闭门、反滤层、金属栅栏的揭煤对比试验，研究煤层瓦斯压力梯度下降速率对突出强度的影响，试验结果表明:突出强度随突出通道渗透性的增加而增加。.所建立的煤层一维渗透失稳判别式和煤层一维渗透失稳数学模型，可解释煤与瓦斯突出的各种动力现象和各项控突措施的作用机制，丰富了土力学渗透失稳理论，为煤与瓦斯突出强度定量预测和创新控突措施提供理论成果；提出的反滤层控突方法的控突效果有待现场试验验证。.共发表论文8篇，其中，SCI期刊论文1篇，获发明专利1项。