A newly constructed open-pit mine has transmission tower foundations for the Yiquan-Yi Line and Jinzhong HVDC Line located approximately 300 meters away on both sides, where slope excavation may induce tilting and subsidence of the power transmission tower foundations, or foundation damage from rockfall impacts. Stereographic projection, limit equilibrium method, and finite element numerical simulation were applied to qualitatively and quantitatively analyze the excavation disturbance zone, slope stability, and rockfall effects on power transmission tower foundations. Analysis results indicate stable slopes at final excavation boundaries, with power tower foundations positioned 69.2–192.9 meters beyond the disturbance zone and outside minimum-safety-factor failure surfaces. Rockfalls from the pit crest primarily roll down into surrounding gullies, with no rocks reaching the vicinity of the power transmission tower foundations on either side of the open pit, which are also situated at higher elevations. The study concludes that mining operations at this new mine will not affect the power transmission tower foundations adjacent to the pit.