Mechanism of rock burst induced within the fully mechanized top coal caving face with overlying knife-shape-like gob and hard thick roof

Irregular upper gobs may increase the risk of rock burst incidents in coal mines. Investigating the rock burst mechanism in the complex mining spatial structure of multi-seam rock bursts is essential for ensuring the safe extraction of coal resources. This study investigated the distribution characteristics of static and dynamic loads on the W1123 working face through a comprehensive approach utilizing theoretical analysis, numerical simulation, and on-site monitoring. The mechanism of rock bursts was analyzed and targeted preventive measures were proposed and applied on-site. The results indicated that the coupled effects of the overlying knife-shape-like gob and thick hard roofs exhibited regional characteristics in the distribution of static and dynamic loads beneath the W1123 working face. When the working face was solely influenced by the “handle” effect of the knife-shape-like gob or concurrently affected by both the “handle” and “blade body”, the lower part of the working face and the coal pillar experienced concentrated static loads and intense dynamic load disturbances. The surrounding rock in the upper gob also demonstrated concentrated static and dynamic loads, with the proximity to the boundary of the knife-shape-like gob resulting in higher dynamic and static loads. When only affected by the “blade body”, the upper surrounding rock of the working face experienced concentrated static loads and was disturbed by dynamic loads. The area of concentrated static loads and dynamic load disturbances in the working face coincided, leading to the manifestation of rock burst from the superposition of dynamic and static loads. Based on the structural characteristics of the knife-shape-like gob, the rock burst types during the mining period of the W1123 working face were sequentially classified as strong dynamic load type, high static load, strong dynamic load type, and high static load type. The risk of rock bursts assessed through on-site monitoring and numerical simulation matched the theoretical analysis outcomes. Rock burst prevention measures were optimized based on the distribution characteristics of static and dynamic loads on the W1123 working face. To mitigate the stress and energy concentration on the roof and coal body, we have enhanced the treatment height and crushing degree of the thick, hard roof while also intensifying coal body blasting and pillar cutting. Following the implementation of these optimized measures, the average event energy released by the surrounding rock of the working face decreased by 54%, and significant energy events were substantially reduced, leading to a significant reduction in the rock burst risk. This study can provide valuable insights for rock burst prevention in mines with irregular upper gobs.