###### Abstract  
The western mining regions of China, known for shallow-buried and high-intensity mining activities, face significant ecological threats due to damage to loose strata and the surface. The evolution of fissures within the loose layer is a critical issue for surface ecological environment protection in coal mining areas. The study employed field measurements, mechanical experiments, numerical simulations, and theoretical analysis, using the 'triaxial consolidation without drainage' experiment to assess the physical and mechanical properties of various strata in the loose layer. Additionally, the PFC(tm) numerical simulation software was employed to construct a numerical model that elucidates the damage mechanisms and reveals the evolution of loose layer fissures and the development of ground cracks. The research findings indicate that during shallow-buried high-intensity mining loose layer fissures undergo a dynamic evolution process characterized by \"vertical extension-continuous penetration-lateral expansion\". As the working face advances, these fissures eventually propagate to the surface, forming ground cracks. The strong force chains within the overlying rock (or soil) layers develop in the form of an \"inverted catenary arch\". As the arch foot and the middle of the arch overlap, fissures propagate along these strong force chains to the surface, resulting in ground cracks. The study elucidates the surface damage patterns in shallow-buried, high-intensity mining, offering theoretical insights for harmonizing coal mining safety with ecological conservation in fragile regions.  
shallow buried coal seam; high-intensity mining; force chain arch; loose seam; ground cracks +
Footnote †: journal:physical and mechanical properties of soils, even when subjected to identical mining-induced stress [10; 11; 12; 13; 14]. Researchers investigated mining damage by applying theories like the 'arch beam structure', plate theory, and the 'parabola' model to elucidate how changes in rock structure affect ground fissure formation mechanisms [15; 16; 17; 18; 19]. However, many researchers pay more attention to the influence of the mobile damage structure on the development of the ground fissure and regard the loose seam as a single uniform medium integrated into the bedrock. Consequently, the potential impact of the internal damage on the development of the ground fissure has received less attention [20; 21; 22; 23; 24; 25].  
The author focuses on the crack evolution in the working face of 20313 in the Gao jialiang Coal Mine, a typical shallow-buried high-strength mining site. A loose layer damage model was developed using PFC2D software (5.0) by analyzing field-measured fracture distribution and production and evaluating various physical and mechanical properties through a 'triaxial consolidation without drainage' approach. This study investigates the crack evolution law and crack formation mechanism within the loose layer. Additionally, the author establishes a method for identifying layer failure instability based on the \"polygonal catenary arch\" theory, providing a theoretical and technical foundation for addressing mining-related damage and protection in eastern regions of China.