Model of Shield-Strata Interaction and Its Implications for Active Shield SettingRequirements

摘要

The paper evaluates factors which influence longwall support and stratainteraction. The longwall system is composed of an immediate and main roof structure and three supporting foundations: (1) longwall panel, (2) powered supports, and (3) gob. The main roof forms a structure that is generally supported by all three foundations, while the immediate roof acts as a beam that cantilevers from the coal face to the powered support. Shield loading involves a complex interaction of both main roof and immediate roof behavior and is a combination of loads produced from convergence of the main roof and displacements of the immediate roof caused by deformations of the cantilevered roof beam. Since the shield stiffness remains constant for all leg pressures and main roof convergence is irresistible in terms of shield capacity, the shield must be able to change the stiffness of the immediate roof or floor structure for shield loading to be sensitive to setting pressures. If the goal is to minimize total shield loading, any active setting force must be offset by reduced passive loading development to justify the active setting loads. Field data suggest that the typical reductions in passive load do not justify the required increases in setting pressure.