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

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.