Measures and effects of eco-geological restoration in well No.4 in the Muli mining area, Qinghai Province, China

ObjectiveThe Muli mining area, located in the hinterland of the Qilian Mountains, Qinghai Province, serves as the source of the Datong River—a major tributary of the Yellow River. This area falls within the alpine permafrost region, exhibiting a sensitive, fragile ecosystem. In the early 21st century, disordered coal mining in this area has caused ecological damage. This has notably posed four challenges in the ecological restoration of well No.4 in this area: (1) high, steep, and unstable slopes of spoil heaps; (2) a large volume of water accumulating in mining pits; (3) permafrost excavation and destruction, and (4) land occupation and meadow destruction by spoil. MethodsThis study simulated the geological structure and properties of original strata from the perspective of geological restoration. Accordingly, it constructed eco-geological layers and performed reconstruction and restoration for varying geobodies. Multiple measures for eco-geological restoration were adopted in well No.4, including (1) roof cutting and unloading of the southern spoil heap from the middle part at the rear of its landslide; (2) constructing a hard base layer of soils on the surface of spoil heaps; (3) cleaning the slopes of mining pit wall and shaping them into steps or platforms; (4) backfilling and permafrost restoration at the bottom of the eastern part of the mining pit; (5) converting water accumulating in the western part of the mining pit into a plateau lake, and (6) introducing artificial soil layers and grass mulching on slopes of spoil heaps and mining pits. These measures have collectively reshaped the post-mining terrain and geomorphology of well No.4. Results and Conclusions The treatment of well No.4 in the Muli mining area involved an area of 16.703 1 million m², a cumulative backfilling volume of spoil reaching 9.160 3 million m³, and a grass mulching area of 2.968 million m². After three years of dedicated ecological restoration, the spoil heaps in well No.4 generally remain stable. The artificial soils, created using spoil, contribute to the vigorous natural growth of grass species and high-quality surface water. This treatment has created a new plateau landscape where the topography, geomorphology, and ecological environment of well No.4 are harmoniously integrated with the surrounding environment. The treatment method and achieved effects of this study offer successful experience and references for both the protection of ecological barriers in alpine regions and ecological restoration in other areas.