Non-Darcy flow seepage characteristics of saturated broken rocks under compression with lateral constraint

Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on seepage characteristics was analyzed. The results show that: (1) Under the same axial stress (12 MPa), the permeability of different lithologic samples increases in the order: gangue < mudstone < sandstone < limestone. The permeability of gangue is 3 magnitudes lower than that of limestone. The absolute value of the non-Darcy coefficient β increases in the order: limestone < sandstone < mudstone < gangue. The non-Darcy coefficient β of limestone, which is positive, is 5 magnitudes lower than that of gangue. (2) With increasing axial stress, the permeability of saturated broken sandstone decreases, and the absolute value of the non-Darcy coefficient β increases. After the axial stress exceeds 12 MPa, the curves of permeability and non-Darcy coefficient β all tend to be stable. (3) With increasing Talbol power exponent, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. (4) With increasing loading, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. When the loading rate is 0.5 kN/s, the non-Darcy coefficient β is positive.