Law of overburden and surface deformation in roof cutting and backfilling mining under thin bedrock in shallow buried coal seam

Under the specific geological conditions of shallow buried coal seams and thin bedrock, the caving method of coal mining can result in irreversible damage to the ecological environment, such as affecting the aquifer structure, causing surface subsidence and creating ground fissures. However, traditional backfill mining faces challenges such as insufficient material, low efficiency and high costs. The paper focuses on the novel ideas of roof cutting and backfilling mining treatment, using Jinjie Mine as the research background. Through theoretical analysis, similarity model experiments and numerical simulation, it investigates the laws of overburden failure, surface movement and deformation under shallow buried and thin bedrock geological conditions when using roof cutting and backfilling mining. The comparative study with the fully mechanized caving mining method shows that the use of roof cutting and backfilling methods can suppress the development of fractures and achieve the effect of reducing subsidence. Before releasing the constraint of the filling gangue column, the maximum direct roof subsidence of the coal seam reached 375 mm, whereas the maximum surface subsidence was 263 mm. After releasing the constraint, the maximum direct roof subsidence of the coal seam reached 541 mm, whereas the maximum surface subsidence was 403 mm. This is significantly smaller than the 2804 mm subsidence observed with the caving mining method. Under the condition of ensuring the filling rate of gangue and lateral constraint, roof cutting and backfilling mining will effectively inhibit the development of a fracture zone and reduce the workload of mine water control. This visual simulation study of the entire backfilling mining process, conducted using similar material model experiments, and the necessary complementary analysis of the actual observed results of the model experiment by numerical simulation, confirms that the roof cutting and backfilling mining method can effectively control surface subsidence and be material self-sufficient.