Seepage calculation method of loose rock mass under mining unloading

To explore the relationship between seepage coefficients of loose rock mass and mining unloading undermining unloading, the calculation method of seepage of loose rock mass undermining unloading is studied in depth. Weathered sandstone is used as a test sample, and a different size of axial pressure is applied to the specimen so that the specimen is subjected to different external forces to form different fissures of loose rock. The seepage-stress coupling model undermining unloading is constructed, and the relationship between fracture permeability coefficient and fracture closure is analyzed. The results show that the back pressure is proportional to the permeability coefficient of a loose rock mass. On this basis, according to the non-linear relationship between backpressure and fracture width during the mining unloading process, the specimen cracks during the mining unloading process are established. The relationship between the unloading permeability coefficient and mining unloading capacity of the loose rock mass is obtained by the equation of opening capacity and unloading capacity and the cubic law. The results show that the permeability coefficient increases slowly with the increase of mining unloading. When mining unloading increases to 60%-80%, the permeability coefficient increases rapidly. Moreover, the increase of mining unloading and pore water pressure of loose rock will also lead to an increase of permeability coefficient, which can play a dangerous early warning role in practical slope application.