Re-crushing process and non-Darcian seepage characteristics of broken coal medium in coal mine water inrush

Abstract

The initiation process of the mine water inrush accident, the essence of this process is the sudden change of the seepage state of the broken coal medium under pressure and the instability of the skeleton. In order to study the re-crushing mechanism and seepage characteristics of the broken coal medium under load, a set of three-axis seepage system was designed independently. Using the steady-state infiltration method, multiple flow factors under different particle size combinations and different stress conditions of the broken coal medium were obtained. The results of the study indicate: in one hand, the reduction of the porosity of the broken coal medium will cause the flow channel to be rebuilt, and the sudden change of flow rate will directly lead to the non-Darcian flow behavior. The early stage of compaction mainly affects the permeability k value, and the later stage of compaction mainly affects the non-Darcian β value; On the other hand, the seepage throat in the broken coal medium may have a sharp increase in its flow rate, leading to a sudden change in the flow pattern. The critical Reynolds number is also used to determine whether non-Darcian flow is formed, and its value in the water inrush system is about 40–133; at the same time, the non-Darcian flow in the broken coal medium conforms to the Forchheimer-type flow law. By analyzing the dependence relationship between factors, a seepage factor representation algebraic relationship suitable for Forchheimer type non-Darcian flow of broken coal medium is given, which can be used as a calculation basis in the prevention and treatment of mine water inrush accidents.

Pressure-Shear Crack Initiation and Expansion Mechanism of Complex Cracked Rock Mass under the Seepage Stress

“…At this stage, many scholars have carried out a lot of research on the positive aspect of seepage. Pang et al [27] independently designed a triaxial seepage system in order to study the recrushing mechanism and seepage characteristics of crushed coal medium under load. Using the steady-state infiltration method, various flow factors of the crushed coal medium under different particle size combinations and different stress conditions are obtained.…”

Experimental study on the permeability of crushed coal medium based on the Ergun equation

“…The non-Darcian factors in the Forchheimer equation have been broadly studied 27 – 29 . The Ergun equation, was the most extensively studied, which was summarised by Ergun based on the theory of pipe flow, and the definition of the mean hydraulic radius.…”

Developmental prediction law of water-conducting fracture zones in shallow buried single coal seams.

“…China's coal resources are widely distributed, rich in reserves, and the hydrogeological conditions are also complex and varied, and most of the mining areas suffer from mine water intrusion, and there are numerous water accidents [1,2,3]. Overburden water-conducting fissures act as roof water-filling channels, connecting the mined coal seam with the upper aquifer.…”