基于含瓦斯软硬煤组合体强度及其蠕变的延期突出发动机制

A hidden and sudden delay outburst of coal and gas will cause heavy casualties and severe economic losses. Most delay outburst locations are characterized by soft-hard coal body. In this project, with soft-hard coal body as studied object, relationship between its strength and influencing factors including the structure dimension, strength of soft coal, strength of hard coal, gas pressure, lateral stress will be researched, and quantitative evaluation method of the strength will be proposed by real triaxial compression tests. Furthermore, relationship between axial and lateral strains and time will be studied in order to construct creep model and constitutive equation, and cracks evolution law will be studied to discover creep failure criteria by real triaxial creep tests. Based on the above researches, theoretical formula for creep damage of the coal body will be obtained which is considered as initial formula for calculating delay time of the outburst. Then, the formula will be corrected by simulation experiments of delay outburst and the final formula will be used to determine the delay time. Then, the goal of revealing mechanism of delay outburst will be achieved. Research results will provide time and space pre-warning for outburst prevention. Thus they have important theoretical significance and practical value.

煤与瓦斯延期突出具有隐蔽性和突发性，可造成重大人员伤亡和财产损失，而延期突出事故发生地点常具有软煤和硬煤组合分布的结构特征。项目以软硬煤组合体为研究对象，通过真三轴压缩实验，研究含瓦斯软硬煤组合体强度与其结构尺寸、软煤和硬煤单体强度、瓦斯压力及侧压的关系，构建含瓦斯软硬煤组合体强度定量表征方法；通过真三轴蠕变实验，研究含瓦斯软硬煤组合体轴向和侧向应变随时间的变化关系，构建蠕变模型并推导本构方程；研究含瓦斯软硬煤组合体蠕变过程中的裂纹损伤演化规律，确定破坏准则；结合蠕变本构方程和破坏准则，推导蠕变破坏时间的理论计算公式，以此作为突出延期时间的初始计算公式，进而通过延期突出模拟实验对其进行校验，获得突出延期时间的最终计算公式。研究成果将揭示含瓦斯软硬煤组合体延期突出发动机制，为工作面防突提供时空预警，具有重要的理论意义和应用价值。

由于煤与瓦斯延期突出事故发生地点常具有软煤和硬煤或岩石（统称阻挡层）组合分布的结构特征，随着工作面的推进，阻挡层的厚度逐渐减小，阻挡层破坏的可能性越来越大，阻挡层发生破坏需要一定的时间，使具有突出危险性的软煤暴露被推迟，故形成煤与瓦斯延期突出。延期突出发生时，人员可能正在工作面附近进行打钻、清渣或支护等作业，从而造成重大人员伤亡。项目建立了延期突出的“软煤-阻挡层”组合体模型，采用六元件粘-弹-塑非线性蠕变模型，以阻挡层破坏的临界应变反推阻挡层蠕变破坏时间，据此确定延期突出时间。项目研究发现，埋深和阻挡层厚度对组合体的蠕变破坏影响较大。埋深越大，阻挡层达到破坏临界应变的时间越短，反映在煤矿浅部开采时延期突出发生次数较少。当一次采掘进尺较大，使余下的阻挡层厚度变小时，延期突出可能很快发生。阻挡层渗透率对组合体瓦斯压力分布有较大的影响，而突出危险性大小与瓦斯初始解吸特征密切相关，说明在石门揭煤过程中，由于岩石封存瓦斯条件好，煤层被揭开后暴露煤体往往具有较高的瓦斯压力，突出危险性较大。研究成果对揭示含瓦斯软硬煤组合体延期突出发动机制和指导煤矿井下防突工作具有重要的理论意义和应用价值。