含裂隙茅口灰岩渗透特性的试验研究

Experimental Study on Seepage Properties of Fractured Maokou Limestone

为了分析不同载荷作用下茅口灰岩的渗流规律,采用MTS多功能岩石力学试验系统对岩样进行定轴压、变围压作用下的渗透特性试验研究,利用瞬态渗透法测试茅口灰岩的渗流特性,采用孔隙压力差单一时间序列,计算出非Darcy流的渗透参数(渗透率、非Darcy流β因子和加速度系数)。研究结果如下:茅口灰岩的裂隙流具有非Darcy效应;在定轴压作用下,随着围压的不断增大,岩样的渗透率不断减小,并趋于平缓;岩样的渗透系数与体积应力呈指数衰减关系,当体积应力较小时,岩体的渗透系数受体积应力作用较为敏感,而当体积应力较大时,对渗透性的影响敏感性降低;渗透系数、体积应力与渗透压差之间满足指数关系;当体积应力从14 MPa增加到32 MPa过程中,非Darcy流β因子在0附近波动,加速度系数在50×10-20m-1附近波动。

Experimental study was carried out on the seepage properties of Maokou limestone samples under the action of the same axial pressure and different confining pressure with MTS multi-function rock testing machine in order to study the seepage regularity of Maokou limestone under different loads, the seepage properties of Maokou limestone were tested by using of the transient osmosis process, and the seepage parameters of non-Darcy flow ( permeability,βfactor and acceleration coefficient of non-Darcy flow) were calculated according to the individual time series of porous pressure gradient. The test results showed that the fissure flow of Maokou limestone had the non-Darcy effect; its permeability gradually decreased and then trended to slow with the increase of the confining pressure under the action of the same axial pressure; the permeability coefficient and volumetric stress of rock samples were in an exponential attenuation relation, when the volumetric stress was small, the permeability coefficient of rock was more sensitive to its volumetric stress, but when the volumetric stress was large, its influence sensitivity to the permeability decreased;the permeability coefficient, volumetric stress and permeation pressure difference met an exponential relation;and in the process of the volumetric stress increasing from 14 MPa to 32 MPa, theβfactor of non-Darcy flow fluctuated near 0 and the acceleration coefficient fluctuated near 50×10-20 m-1.