为了识别采空区应力加载对破碎煤岩空隙率的影响.基于采空区应力恢复及空隙率对煤自燃影响角度.分析了采空区空隙率对煤自燃发生中的漏风强度.氧气浓度分布.蓄热环境的影响.通过对恒昇采空区破碎煤体的压实实验.测试了其应力应变及空隙率变化特征.结合分形理论.建立了承压颗粒煤分形空隙率模型.明确了分形模型的初始参数.并对实验数据及理论计算数据进行比较.结果表明:① 在应力作用下.破碎煤体发生压实变形.造成颗粒级配发生变化.进而造成分型维数增大与空隙率发生变化.说明随工作面推进及采空区应力逐渐恢复状态下.采空区破碎煤体空隙率呈现动态变化,② 通过测试原始煤样与破碎后煤样粒径分布与级配变化.获得了承压破碎煤体的分形维数.发现承压破碎煤体分形维数增大则说明受载煤样更加破碎.在应力加载状态下其空隙率逐渐减小,③ 通过分形理论与承压破碎煤体的应力应变关系.建立了承压颗粒煤的分形空隙率理论模型.理论计算结果与实验结果误差在0.028-0.106.可满足工程需要,④ 分析了该模型的使用条件.在获得破碎煤岩应力应变函数及应力加载路径的前提下.该模型可对任意状态下的空隙率进行预测.

In order to identify the influence of stress on the porosity of broken coal in goaf,based on the compacted environment of residual coal in gob,the influence of goaf porosity on air leakage intensity,oxygen concentration distribution and thermal storage environment in coal spontaneous combustion was analyzed from the point of stress recovery in goaf and the effect of porosity on coal spontaneous combustion. Through the compaction experiment of broken coal samples of Hengsheng goaf,the change characteristics of stress-strain and porosity were tested. Combining with fractal theory,the porosity fractal model of the compacted coal particles was established,the initial parameters of the fractal model were determined,and the theoretical calculation and the experimental data were compared. The results show that:① under the action of stress,the compaction deformation of granular coal occurs,resulting in the change of particle gradation,the increase of fractal dimension and the variation of porosity. It indicates that with the advance of the working face and the action of the stress recovery,the porosity of the broken coal body in the goaf presents a dynamic change. ② With the test of the particle size distribution and gradation changes of original coal sample and broken coal sample,the fractal dimension of the coal sample is obtained. The increase of the fractal dimension of the broken coal indicates that the loaded coal sample is more broken,the porosity decreases gradually under the stress loading.③ Based on the fractal theory and the stress-strain relationship of crushed coal under pressure,the fractal porosity theoretical model of granular coal under pressure is established. The porosity error of the theoretical calculation and experimental results is between 0.028 and 0.106 by the relationship between fractal theory and the stress-strain of pressure bearing broken coal body,which meet the requirements of engineering,and the model is relatively reliable. ④ The application conditions of the model are analyzed,the model can predict the porosity change dependent on the premise of mastering the stress-strain function and stress loading path of broken coal and rock.

1 空隙率对煤自燃进程影响分析

   1.1 覆岩垮落与堆积

   1.2 空隙率与煤自燃关系

2 承压破碎遗煤的分型模型

   2.1 遗煤堆积空隙率分形模型

   2.2 承压破碎煤体空隙率演变模型

3 承压破碎煤体空隙率实验

   3.1 实验煤样及方法

   3.2 原始煤样分形维数确定

   3.3 承压破碎煤体的分形维数

   3.4 模型与实验结果对比

   3.5 承压破碎煤体空隙率预测方法

4 结论