含瓦斯煤渗透率理论分析与试验研究

THEORETICAL ANALYSIS AND EXPERIMENTAL STUDY ON PERMEABILITY OF GAS-BEARING COAL

从孔隙率的基本定义出发,充分考虑煤基质吸附瓦斯膨胀、热弹性膨胀、受瓦斯压力压缩对其本体变形的影响,首先给出煤体孔隙率与体积应变、温度及瓦斯压力之间的函数关系,再以Kozeny-Carman方程为桥梁,建立扩容前压缩条件下综合考虑有效应力、温度及瓦斯压力共同影响的渗透率动态演化模型。相关试验数据验证表明,所建立的渗透率理论模型具有良好的适用性,能反映出一定条件下的渗透率演化趋势。试验研究表明:煤体孔隙发育程度与渗透率具有较好的一致性,渗透率随孔隙发育程度的增高而增大;当温度和瓦斯压力一定时,渗透率随有效应力的增大而减小,并且瓦斯压力越低减小趋势越明显;有效应力和瓦斯压力一定时,渗透率随温度升高而减小,但其减小幅度基本不受有效应力变化的影响;温度和有效应力一定时,渗透率随瓦斯压力的升高呈先急剧减小而后逐渐平缓的趋势。含瓦斯煤渗透率与有效应力、温度和瓦斯压力之间关系的研究,为有温度场参与的多场耦合问题的研究提供理论基础,也为高温矿井瓦斯抽放率的提高提供技术支持。

From the basic defination of the porosity,the absorption gas expansion,thermoelastic expansion of coal matrix and the influnce caused by gas pressure on coal matrix body dirtortion are considered fully.After showing the function relation between coal porosity and volumetric strain,temperature,and gas pressure,by using Kozeny-Carman equation,the dynamic evolvement model of permeability which is comprehensively influenced by effective stress,temperature,and gas pressure is established before expansion and under the condition of compression.Correlative test data show that this model has good applicability,and can reflect the development of the porosity under certain condition.The study shows that：porosity development degree and permeability of coal have good consistency,and the permeability increases as the porosity development degree increases;when temperature and gas pressure are fixed values,porosity reduces as the effective stress increases,meanwhile the tendency of the reducement is more obvious when the effective stress is smaller;when the effective stess and gas pressure are fixed values,porosity reduces as the temperature increases,however,its decrescent extent is basically not influenced by effective stress;when temperature and effective stress are fixed values,the permeability of coal reduces rapidly firstly and slowly whereafter with gas pressrure increasing.The study of the relationship between gas-bearing coal permeability and effective stress,temperature and gas pressure provides the theoretical foundation for the study of multi-field coupling problem including temperature field.It gives technical support for increasing efficiency of gas drainage in high temperature mine.