Abstract:
This study aims to explore the mechanisms underlying the strong strata behavior in the presence of high-position confined water. To this end, a physical model incorporating a confined water testing system was developed through physical simulation to analyze the fracture and movement characteristics of high-position confined water. The experimental findings reveal that when high-position confined water is present, the strata controlling the rock pressure of the working face transitions from the first sub-key strata to the high main key strata. Besides, the initial and periodic fracture steps of the high main key strata diminish substantially, with the fracture position migrating toward the coal wall. In the strata below the aquifer (high main key strata), integrated composite fracture characteristics from top to bottom are observed, and the fracture position of the roof advances from the rear of the roof control area to the coal wall. During composite roof fracture, the fracture development height, maximum roof displacement, and strata fracture angle increase substantially by 743%, 509%, and 27%, respectively, leading to severe roof weighting. These findings shed light on the underlying causes of the strong strata behavior. Additionally, the action of high-position confined water notably expands the concentration range and magnitude of advance abutment pressure within the working face. Specifically, the average increases in the range of the front abutment pressure rise zone, the peak abutment pressure, and the range of the rear abutment pressure rise zone for the first and second sub-key strata and the high main key strata reach 611%, 33%, and 124%, respectively.