Study on restoration technology for the permafrost eco-geological layer in the alpine Muli coal mining area on the Qinghai Plateau

Permafrost plays a critical role in maintaining ecological stability in alpine regions. However, in ecological restoration practices for coal mining areas in alpine permafrost regions, the restoration and conservation of permafrost have received insufficient attention for an extended period, and research in this area remains notably weak. Taking the ecological rehabilitation project of the Muli coal mining area as a case study, and drawing upon the concept of emulating the vertical seasonal variations, stratigraphic structure, ground temperature, geological processes, and ecological functional differences of the pristine permafrost layers, this study adopts an innovative integrated perspective of ecology and geology to construct a tripartite permafrost eco-geological layer profile model to support permafrost restoration. Distinct from most permafrost hazard mitigation efforts in infrastructure engineering within permafrost regions, this study proposes key technical parameters for permafrost restoration tailored to different structural layers, thereby establishing and filling the technical gap in vertically extensive permafrost restoration in open-pit coal mines, aiming to facilitate the rapid restoration of permafrost in open-pit mines within alpine regions through artificial intervention measures. Monitoring data from test pits and borehole ground temperature measurements indicate a notable upward refreezing of the permafrost table in the restored area, with refreezing rates ranging from 0.7 m/a to 1.65 m/a, demonstrating the effectiveness of the proposed permafrost eco-geological layer rehabilitation technique. This approach and the associated technologies are expected to provide a methodological reference for permafrost restoration and ecological rehabilitation in alpine open-pit coal mines and in permafrost regions more broadly.