Ground fissure development regularity and formation mechanism of shallow buried coal seam mining with Karst landform in Jiaozi coal mine: a case study

A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform, shedding light on the development type, geographical distribution, dynamic development process, and failure mechanism of these ground fissures by employing field monitoring, numerical simulation, and theoretical analysis. The findings demonstrate that ground fissure development has an obvious feature of subregion, and its geographical distribution is significantly affected by topography. Tensile type, open type, and stepped type are three different categories of ground fissure. Ground fissures emerge dynamically as the panel advances, and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position. Ground fissures present the dynamic development feature, temporary fissure has the ability of self-healing. The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded, and the development scale is a dynamic development stage of “closure → expansion → stabilized” on the basis of the original development scale. From the perspective of topsoil deformation, the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established, the development criterion considering the critical deformation value of topsoil is obtained. The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development, and the interaction between slope activity and ground fissure development is expounded. These research results fulfill the gap of ground fissures about development regularity and formation mechanism, and can contribute to ground fissure prevention and treatment with Karst landform.