基于分形理论的承压破碎矸石非Darcy渗流特性研究

Study on non-Darcy seepage characteristics of load-bearing crushed gangue based on fractal theory

为探究采空区充填破碎矸石在上覆岩层作用下的非Darcy渗流特性,利用自主研发的破碎岩石渗流试验系统,采用稳态渗透法对4种不同初始级配的承压破碎矸石进行单轴侧限压缩及渗流试验,得到破碎矸石在不同有效应力下的孔隙度、分形维数、渗透率、欧拉数以及非Darcy渗流过程中的能量耗散规律。研究表明:在高渗透压和高孔隙度下,流体的流速较快导致非线性影响因子E值远大于0.1,此时表现出高速非达西渗流特征;孔隙度随有效应力的变化过程可分为2个阶段,当Talbot幂指数n值趋于0.4时,各粒径区间的颗粒质量配比良好,易被压实;随着分形维数的增大,颗粒破碎程度加剧,岩样渗透率呈线性减小趋势;推导出欧拉数与流速之间是呈反比关系,流速增大流体的动量传递逐渐减小。

In order to investigate the non-Darcy seepage characteristics of crushed gangue filling in the goaf under the action of the overlying rock layer, the self-developed crushed rock seepage test system is utilized to carry out uniaxial lateral limit compression and seepage tests using the steady state permeability method on four kinds of pressurized crushed gangue with different initial grades, and to obtain the porosity, fractal dimensions, permeability, Euler's number, and the energy dissipation law in the non-Darcy seepage process of the crushed gangue under different effective stress conditions. The study shows that: under high osmotic pressure and high porosity, the fluid flow rate is faster, resulting in the E value is much larger than 0.1, at this time, it shows the characteristics of high-speed non-Darcy seepage;the change process of porosity with the effective stress can be divided into two phases, when the n value tends to be 0.4, the particles of each size interval have a good mass ratio, and it is easy to be compacted;with the increase of fractal dimension, the degree of particle fragmentation is increased, and the permeability of the sample is linearly decreasing;it is deduced that there is an inverse relationship between the Euler number and the flow rate, and the momentum transfer of the fluid gradually decreases with the increase of flow rate.