Evaluation of mining and strata-surface control in deeply buried thick coal seams under thin bedrock

To achieve green and efficient mining of deeply buried thick coal seams under thin bedrock, this study takes the Zhaogu No.2 Mine as the engineering background and employs theoretical analysis, laboratory experiments, and field measurements. The technologies and equipment, technical difficulties and corresponding solutions, and economic benefit indicators under multi-slicing mining, large-cutting-height mining, and top-coal caving mining are compared. An adaptability evaluation model for mining methods is established based on economic and mining-technical indicators. A surface subsidence prediction method for extra-thick alluvium is proposed. Results show that top-coal caving mining exhibits the highest adaptability, followed by large-cutting-height mining and multi-slicing mining shows the weakest adaptability. The dynamic load method established based on the instability characteristics of the overburden caving arch can be used to guide the selection of hydraulic supports. Grouting-based modification and reinforcement at the bottom of the alluvium can enhance the integrity and water-resisting capacity of the thin bedrock-alluvium interface, promoting the formation of the towering roof beam structure, and weakening the concentrated transfer of thick alluvium load to the supports in the working face. The established surface subsidence prediction model reveals the mechanical mechanism of a surface subsidence exceeding 1.0. This study provides references for mining method selection, strata control, and subsidence mitigation in deeply buried thick coal seams under thin bedrock.