循环加卸载作用下完整和裂隙煤体渗透性演变规律研究

Study on permeability law of intact and fractured coals under cyclic loading and unloading

为了得到煤层群重复采动作用下被保护层的渗流特性,总结出被保护层所承受的应力路径,分为加载、卸载和恢复3个阶段,基于自制的受载煤体注气驱替瓦斯测试仪,进行模拟重复采动影响渗流实验,分析完整和带有贯穿裂隙2类煤样在此路径下的渗流规律。研究结果表明:(1)重复采动作用会对煤体产生损伤,采动次数越多,渗透率变化越明显,卸载阶段是煤样渗透率变化的主要阶段。(2)加载阶段两类煤样的应力敏感性随采动次数的增加而降低,卸载和恢复阶段的应力敏感性随采动次数增加而升高,第一、二次采动作用完整煤样应力敏感性大于裂隙煤样,第三次采动裂隙煤样大于完整煤样。(3)第一、二次采动为两类煤样的压实阶段,第三次采动为增透阶段,且重复采动对裂隙煤样的增透作用大于完整煤样。

In order to obtain the seepage characteristics of the protected layers under repeated mining,this paper summarizes the stress path of the protected layers as three stages of loading,unloading and recovery,and carries out simulating repeated mining seepage tests by a self-made gas injection and displacement gas tester to analyze the seepage law of two types of intact and fractured coal samples.The results show that the more the mining times,the more obvious the permeability changes,and the unloading stage is the main stage of permeability change.The stress sensitivity of two kinds of coal samples decreases along with increasing the mining times in the loading stage,while increases with increasing the mining times in unloading and recovery stages.The stress sensitivity of the intact coal samples under the first and second mining is greater than that of the fractured coal samples,while the stress sensitivity of the fractured coal samples under the third mining is greater than that of the intact coal samples.The first and second mining is the compaction stage of two types of coal samples,and the third mining is the permeability increasing stage.The permeability increasing effect of the third mining is greater than that of the first and second mining,and the permeability increasing effect of repeated mining on the fractured coal samples is greater than that of the intact coal samples.