Inner dumps formed by mining activities were prone to soil erosion. Slope improvement is an effective means to control soil erosion and ecological restoration. However, little research has been done on the effect of improver application methods on the effectiveness of amendments. This paper combined similar theory to build an indoor inner dump model, used simulated rainfall tests and microstructural analysis to investigate the erosion resistance and water retention of the inner dump under different methods of PAM. The results showed thattrace source erosion and side erosion didn't occur in the inner dump model without PAM applied. Spreading PAM powder granules and spraying PAM gum liquid could reduce the internal earth pressure and pore water pressure of the inner dump to rainfall. Spraying PAM gum liquid could form a uniform film that can more effectively prevent rainfall infiltration. The carboxyl groups generated by the reaction of PAM and water could enhance the adhesion of clay minerals in the inner dump. The hydrogen bonds in the PAM gum liquid could connect water molecules, thereby forming interlocking soil particle aggregates, which enhance the anti-erosion ability of the inner dump. Spreading PAM powder granules and spraying PAM gum liquid can reduce the porosity of the improved soil, but spraying PAM gum liquid could reduce the porosity by 56.44%, which can effectively reduce water loss and had the best water retention. Therefore, spraying PAM gum liquid had better anti-erosion ability, which could lay the foundation for the ecological restoration of the inner dump.

Overlying river can accelerate the creep of the inner dump, so to master the creep characteristics of the overlying river can provide a theoretical basis for mine safety and discharge optimization. Taking the overlying river inner dump of Yuanbaoshan open-pit coal Mine in China as the research object, a design scheme is proposed to divide it into rolling zone and non-rolling zone. Based on the creep model obtained by in-situ deformation monitoring and laboratory rheological test, the creep evolution law and deformation of overlying channel after soil discharge, slope morphology and advancing position are simulated and analyzed. The results showed that the creep variable in the (non-) rolling zone had a nonlinear upward trend with time, and the initial upward trend was large. The maximum vertical and horizontal creep in the rolling area was located in the middle and upper part of the rolling line, while the maximum vertical and horizontal creep in the dump was located in the middle and upper part of the non-rolling area, respectively. The post-construction settlement and horizontal discharging increased with the increase of the discharge height, and the convergence creep of the top ten years after construction increased approximately linearly with the decrease of the distance from the shoulder of the inner dump. The rolled sand and gravel backfill belonged to the foundation of uniform settlement deformation in general, and the change of slope shape had little effect on the deformation of the slope top in the rolled area. The geoglage elongation in the dam area met the requirements. On the premise of ensuring the stability of the dump, the slope angle of the inner dump can be appropriately increased to increase the capacity of the inner dump. The research results can provide guidance for the construction of inner dump in open pit.