卸围压速率和瓦斯压力对原煤力学和渗流规律的影响
Influence of unloading confining pressure rate and gas pressure on mechanics and seepage properties of raw coal
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摘要: 深部煤炭开采过程中，由于工程扰动，地应力发生复杂变化，由此导致煤岩力学性质、渗透率特性等随之改变。基于此，进行了煤样在轴压一定，不同卸围压速率、不同瓦斯压力条件下的流固耦合试验。研究了煤样在不同应力卸围压速率、瓦斯压力作用下的力学和渗流特性；分析了三轴卸围压和不同瓦斯压力条件下原煤的变形、强度、力学参数变化规律；揭示瓦斯的分阶段演化特性。结果表明：随着围压卸载速率、瓦斯压力的不断增加，煤样破坏时的变形、塑形平台逐渐增强；煤样的变形模量、侧向变形系数及破坏时的有效围压均随着卸围压速率、瓦斯压力的增加而逐渐降低；轴压加载阶段，由于原生裂隙被压密，渗透率逐渐降低，在围压卸载阶段，由围压卸载引起的原生孔隙裂隙扩张、高偏应力差引起的煤样新生裂隙导致裂隙总量增加，渗透率逐渐增大。Abstract: In the process of deep coal mining, due to engineering disturbances, the ground stress undergoes complex changes, which leads to changes in the mechanical properties and permeability characteristics of coal. In this paper, the fluid-solid coupling tests of coal samples under certain axial stress, different unloading pressure rate and different gas pressure conditions were carried out. The mechanical and seepage characteristics of coal samples under different stress unloading pressure rats and gas pressures were studied. The results shown that with the increase of unloading rate and gas pressure, the deformation and plasticity platform of coal samples were gradually strengthened. The deformation modulus, lateral deformation coefficient and effective confining pressure of coal samples decreased with the increase of unloading pressure and gas pressure. During the axial compression loading phase, the permeability was gradually reduced due to the compaction of the primary fractures. In the confining pressure unloading stage, the expansion of primary pore fissure caused by confining pressure unloading and the new fissure caused by high deviated stress difference lead to the increase of total fissure and permeability.
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