含瓦斯构造煤卸围压作用渗透性变化特征试验研究

Experimental study on characteristics of permeability variation for tectonic coal containing gas under unloading confining pressure

针对含瓦斯煤轴压恒定卸围压渗透性演化规律,以新登煤业二1煤原煤样为研究对象,利用自主研发的含瓦斯煤岩三轴应力蠕变渗流试验装置,开展不同围压下轴向应力恒定卸围压渗流测试试验。基于实验结果表明:构造煤在应力加载阶段渗透率降低,且轴压围压同时加载,渗透率变化与轴向应变符合线性变化,轴压加载阶段,渗透率与轴向应变符合负指数函数变化规律;围压卸载阶段,渗透率在卸围压过程中一直减小,随着轴向应变的增加,渗透率出现反弹,但未出现突变现象,渗透率增加阶段与时间变化符合退化的负指数函数关系;构造煤渗透率卸围压失稳后,渗透率没有出现突变原因认为煤样中没有形成较大的有效渗流通道,且在一定的有效应力作用下瓦斯渗流的有效通道出现自愈合现象。

Aiming at the evolution regulations of permeability for coal containing gas under unloading confining pressure with constant axial pressure , taking the raw coal samples 二1 coal in Xindeng Coal Industry as the research object , the test experi-ments on seepage during unloading different confining pressure with constant axial pressure were carried out by using the self -developed experimental apparatus on three axis stress creep seepage for coal containing gas .The results showed that the per-meability of tectonic coal in the stress loading stage decreases , and when loading the axial pressure and confining pressure simultaneously , the change of permeability accords with linear change against axial strain .In the stage of loading axial pres-sure , the permeability accords with the change law of negative exponential function against axial strain .In the stage of unloa-ding confining pressure , the permeability always decreases in the process of unloading confining pressure .With the increase of axial strain , the permeability rebounds , but without mutation phenomenon , and the permeability in the increasing period accords with the degraded negative exponential function against time .After the instability of tectonic coal under unloading confining pressure , the reasons of without mutation for permeability is that larger effective seepage channels have not been formed in the coal samples , and the self-healing phenomenon has appeared in effective channels of gas seepage under the effect of certain effective stress .