A review of the mass-loss-induced non-Darcy seepage and seepage suffosion in the fractured zone: the concepts discrimination and connection

Water inrush disasters in coal mines and tunnels are mostly related to fractured zones, which not only cause great economic losses and casualties but also seriously affect coal mine production. Therefore, research on the mechanism of water inrush is an urgent need for the coal-mining industry, which should be carried out effectively to prevent the occurrence of water inrush. Due to the excavation activities, the rock mass in the fractured zone is prone to structural deformation and fractured, and the non-Darcy seepage occurs with particle migration and structural deformation, i.e., seepage suffusion happens. With the continuous development of seepage suffosion, the seepage field of rock mass changes, which is very easy to cause non-Darcy seepage instability, which is the essence of seepage suffosion. This paper describes the seepage suffosion and the non-Darcy seepage instability of the broken rock mass, distinguishes the related concepts, and reviews the research progress. Though previous studies have creatively given some criteria from many angles, for instance, βk2 < 3.90 × 10−12 m3, r < 4.90%, $${m}_p^{\prime}\ge$$ 100 gs−1 m−3, etc., it was not enough to solve the related engineering problems. Because the mining activity in the rock mass is a complex physical and mechanical process, solid, liquid, and gas coexist under the coupling action of multiple fields, such as the stress field, temperature field, and seepage field. Therefore, it proposes that, in the further study of water inrush mechanism, (1) the stable/unstable deformation, the failure state, failure conditions, and failure laws of rock mass under the coupling action of stress, groundwater, gas, temperature, etc. are necessary to be fully considered; (2) the non-Darcy seepage process needs to be described in suitable theory; (3) more disciplines and more advanced methods need to be integrated and adopted; (4) simpler judgment methods and accurate judgment standards need to be put forward. It helps to penetrate the mysteries of water inrush disasters in the coal mines and tunnels with fractured zones.