考虑含水率影响的煤岩变形及渗透率模型

Deformation and permeability model of coal and rock considering moisture content

  • 摘要: 煤矿开采深度不断增加,煤层瓦斯含量升高导致动力灾害逐渐增多,给煤矿安全开采带来严峻考验。对于瓦斯在煤层中流动的研究一直以来都备受关注,其中渗透率正是影响煤层中瓦斯流动的关键参数之一。因此,为准确模拟开采环境变化导致的煤岩变形及渗透特性变化,利用含瓦斯煤热-流-固耦合三轴伺服渗流装置,开展不同含水条件下孔隙压力升高过程中煤岩渗透特性的试验研究,建立考虑含水率的吸附方程和吸附-渗透率模型,探讨含水率和孔隙压力共同作用对煤岩变形及渗透特性的影响。研究结果表明:① 孔隙压力升高过程中,径向应变及轴向应变随孔隙压力的升高均呈降低趋势,瓦斯流量的变化呈上升趋势,煤基质由于吸附瓦斯产生膨胀变形,体积应变逐渐减小。② 当含水率恒定时,随着孔隙压力的升高,瓦斯吸附量随孔隙压力增大先增大而后趋于平缓,产生的吸附变形的变化趋势与其相同;当孔隙压力恒定时,煤岩的吸附量和吸附变形均随着含水率的增大而减小。③ 在恒定含水率条件下,煤岩渗透率曲线随孔隙压力的升高先减小后趋于平缓;而在相同的孔隙压力条件下,随含水率的增加,煤岩渗透率整体逐渐减小,而且含水率越大孔隙压力对渗透率的影响越弱,水分子对渗透率的影响越强。④ 构建了考虑含水率的吸附量计算方程,并在此基础上进一步构建考虑含水率煤岩吸附-渗透率模型,其中所计算的渗透率值与试验所测结果基本一致,反映了煤岩渗透率变化规律。

     

    Abstract: The depth of coal mining is increasing,and the increase of gas content in coal seams leads to the gradual in- crease of dynamic disasters,which brings severe challenges to the safe production of coal mines. Research on the flow of gas in coal seams has always been a concern and the permeability is one of the key parameters affecting gas flow in coal seams. With the application of the coal containing gas heat-fluid-solid coupling device of three axis servo seepage, it can simulate the deformation and seepage characteristics of coal mining caused by the environment through the ex- perimental studies on the permeability of the process of the coal when the pore pressure are under different saturated conditions. Then considering moisture content,the authors establishes an adsorption equation and adsorption-permea- bility model so as to model the common effect of water content and pore pressure on the deformation and permeability characteristics of coal. The results show that:① in the process of pore pressure increase,the radial strain and axial strain decrease with the pore pressure increases,and the change of gas flow increases. Due to gas adsorption,coal ma- trix swells,and the volumetric strain decreases gradually. ② When the water content is constant,and with the increase of pore pressure,the gas adsorption capacity increases first and then levels off. The coal gas adsorption capacity and deformation decrease with the increase in moisture content when the pore pressure is constant. ③ Under constant mois- ture conditions,coal permeability curve decreases first and then levels off with the pore pressure increase. Under a con- stant pore pressure,with the increase of moisture content of coal,the permeability decreases gradually,the higher mois- ture content of pore pressure,the less effect on the permeability by pore pressure,the stronger effect on permeability by water molecules. ④ The calculation formula of the adsorption amount considering the water content is constructed,and on this basis,the coal adsorption-permeability model considering the water content is further constructed. The calculat- ed permeability value is basically consistent with the experimental results,which reflects the variation law of coal per- meability.

     

/

返回文章
返回