Innovative for farmland reclamation: Optimizing earthwork allocation and elevation in mining-induced subsidence

Coal mining activities have resulted in significant farmland degradation in the Yili Coal-Grain Composite Area (CCA) of China. In this study, mine reclamation was investigated to address mining subsidence caused by shallow-buried and ultra-thick coal seams in CCA. In Yili No.1 Coal Mine, the subsidence morphology and Farmland damage boundaries were predicted to optimize a reclamation elevation method. Four reclamation schemes were conducted by three geological profiles, and earthwork allocation schemes were formulated by varying elevation controls. The different reclamation strategies were analyzed to optimize the mine reclamation. The results show that: 1) Topographic gradient causes asymmetric earthwork distribution, with southern reclamation zones requiring significantly more material than northern areas; the three-terrace scheme fails to reduce elevation differences in steeper southern sectors; 2) Earthwork volume and sub-area segmentation exhibit non-monotonic behavior: Optimizing sub-area layouts along the dip-directional elevation gradient-rather than increasing division density-substantially minimizes earthwork demands, underscoring geomorphic alignment as a critical design factor; 3) The required earthwork volumes are as follows: Scheme Scheme 4 < Scheme 1 < Scheme 3 < Scheme 2. Earthwork allocation rankings are: Scheme Scheme 3 < Scheme 1 < Scheme 2 < Scheme 4. Scheme 1 balances overall earthwork and partitioning, while scheme 4 minimizes material transport through adaptive terrain integration; 4) Morphology-based reclamation, compliant with national farmland standards, optimally mitigates elevation differences and reduces earthwork, offering a cost-effective solution for sloped subsidence areas. These findings guide reclamation optimization in Coal-Grain Composite Area, prioritizing topographic adaptability and engineering efficiency.