三轴加载条件下隔水岩层渗透特性试验研究

Experimental Study on Permeability Characteristics of Water-insulating Rock Formations under Triaxial Loading Conditions

隔水岩层采动影响下的渗透性能是评估水体下采煤安全与否的关键指标。为研究采动隔水岩层渗透性演化规律,通过进行三轴加载渗流试验,研究围压、水压对不同岩性隔水岩样承压破坏过程中渗透性演化的作用规律。结果表明:(1)隔水岩样三轴加载条件下渗透性演化规律与岩石内部裂隙、空隙压实程度及新生裂隙发育演化密切相关,岩石承载压缩过程中渗透性演化对应分为4个阶段;(2)围压、水压增大的降渗效果随轴压增大而减弱,围压、水压增大对岩石渗透系数的减弱呈现出非线性的特点;(3)岩石渗透性由大至小的顺序为中砂岩、细砂岩、砂质泥岩,岩性及矿物组成是影响围压、水压对岩石渗透系数的作用效果的主要因素。研究成果可为隔水岩层采动影响下隔水性能评价提供理论依据。

The seepage performance of water-insulating rock formations under the influence of mining movement is the key index to evaluate the safety of coal mining under water body.In order to study the permeability evolution law of mining water-insulating rock formations,the effect of confining pressure and water pressure on the permeability evolution of different lithologic water-proof rock samples during the process of pressure failure was studied through triaxial loading seepage test.The results show that:(1)Under triaxial loading,the permeability evolution law of water-proof rock samples is closely related to the compaction degree of cracks and voids in rock and the development and evolution of new cracks,the evolution of rock permeability in the process of bearing compression can be divided into four stages;(2)The decreasing permeability effect of confining pressure and water pressure increases with the increase of axial pressure,and the decreasing permeability coefficient of rock with the increase of confining pressure and water pressure presents nonlinear characteristics;(3)The order of rock permeability from large to small is medium sandstone,fine sandstone and sandy mudstone.Lithology and mineral composition are the main factors affecting the effect of confining pressure and water pressure on rock permeability coefficient.The research results can provide a theoretical basis for the evaluation of water-retaining performance of water-insulating rock formations under the influence of mining.