围压对液氮冷浸煤样力学和渗透性特征的影响研究

Study Effects of Confining Pressure on Mechanical and Permeability Characteristics of Liquid Nitrogen Soaking Coal Samples

为探究围压对液氮冷浸后煤样的力学特征及渗透率变化的影响,对液氮冷浸煤样进行不同围压下的三轴渗流实验,并与未冷浸处理煤样的渗透率进行对比,结果表明:液氮处理后煤样渗透率增加了118.6%~432.5%,液氮致裂增透效果明显。煤的受压破坏过程分为压密、弹性、屈服、破坏4个阶段,不同围压下煤样的渗透率都在弹性阶段达到最小并在屈服阶段快速增大。煤的弹性模量、抗压强度均与围压正相关,而初始渗透率与围压为负指数关系。煤的力学性质和渗透性在不同围压下的差异是因为围压对裂隙的产生和发展起限制作用。

To explore the influence of confining pressure on the mechanical characteristics and permeability change of coal samples after liquid nitrogen soaking, triaxial seepage experiments were carried out on liquid nitrogen-soaked coal samples under different confining pressures and compared with the permeability of unsoaked coal sample. The results show that the permeability of coal samples after liquid nitrogen soaking increases by 118.6 %-432.5 %. The failure process of coal is divided into four stages: compaction, elasticity, yield, and failure. The permeability of different coal samples reaches the minimum in the elastic stage and increases rapidly in the yield stage. The elastic modulus and compressive strength of coal are positively correlated with confining pressure, and the initial permeability is negatively exponential with confining pressure. The difference of mechanical properties and permeability of coal under different confining pressures is because confining pressure restricts the generation and development of cracks.