Dynamic Load Characteristics and the Pressure Reduction Caused by the Cutting Seam on the Roadside Roof of a Large Mining Height Longwall Face in a Shallow Coal Seam

Abstract

Gob-side entry formed by lagged roof cutting is a new mining technology without a coal pillar, which is applied for the first time under shallow thick coal seam conditions. During the process of working face advancement, there are obvious divisions of the dynamic load characteristics of the hydraulic supports at different positions on the non-roof-cutting side (from the haulageway to the middle of the working face). Among them, the hydraulic support in the middle of the working face has a large dynamic load coefficient. Due to lagged roof cutting, the hydraulic support load on the roof-cutting side (from the air-return roadway to the middle of the working face) is affected to varying degrees. The first half of the paper introduces the above characteristics of the non-roof-cutting side. The common points of the overlying strata on the working face are obtained by analogical induction, and through mechanical modeling and formula derivation, the phenomenon of the large dynamic load coefficient of the hydraulic support in the middle of the working face is explained. In the latter part of the paper, the two mining technologies without a coal pillar, advanced roof cutting and lagged roof cutting, are briefly introduced; the differences in load reduction characteristics between the two types of cutting methods are compared; and the reasons for the different points are analyzed.