Reshaping of nearnatural landform of the internal dump in the grassland openpit mine based on HPCS

Openpit mining is an important mining method in China’s grassland mining areas. However, the traditional landform of “terraced field” inner dump formed in the process of mining and dumping is faced with problems such as large land area, landscape fragmentation and soil erosion. The naturebased solution (NbS) is based on the natural landscape and has the unique advantage of integrating the original landscape of the mine. Based on the existing technologies and team achievements, in order to build the inner dump landform that is integrated with the surrounding natural topography, a nearnatural landform reshaping model of the inner dump was proposed based on a hydrological preserved curved surface (HPCS). In this paper, the Heishan openpit mine in Xinjiang was selected to construct a nearnatural design landform with HPCS (NNDL_HPCS) as the experimental group, and the NNDL with surface adjustment surface (NNDL_SAS), pristine natural landform (PNL) and traditional design landform (TDL) were used as the control group. Combined with the GIS and CLiDE model, the improvement effects of the NNDL_HPCS on geomorphic fusion, earthwork allocation and soil water erosion resistance were simulated and evaluated. The results showed that:Based on the HPCS nearnatural landform reshaping model of the inner dump, the DEM of the premining surface, the roof and floor of the mining subarea under the preset mining cycle was used to automatically solve the available earthwork for filling and obtained the surface design elevation of the filling subarea. In terms of geomorphic fusion, the NNDL_HPCS was closer to the PNL than that of the NNDL_SAS and the TDL. The total variance of the NNDL_HPCS relative to the PNL was 50.37% and 37.92% lower than that of the NNDL_SAS and the TDL, and the natural hydrological retention rate was 2.85% and 8.53% higher than that of the NNDL_SAS and the TDL, respectively. In terms of earthwork allocation, the average earthwork distance of the NNDL_HPCS was 4.99% and 5.05% higher than that of the NNDL_SAS and the TDL respectively. In terms of soil water erosion resistance, the NNDL_HPCS can reduce water erosion by 55% compared with the NNDL_SAS and 72.6% compared with the TDL in 10 years, which can significantly improve the water erosion resistance of inner dump topsoil.