Hazards and Treatment of Collapsible Loess Foundation on Ultrahigh Voltage Transmission Lines

With the development of ultrahigh voltage transmission line construction in northwest China, an increasing number of overhead transmission lines are crossing the loess regions. Ensuring the stability of electricity transmission towers and mitigating the risk of collapse are crucial prerequisites for the construction of transmission lines. Taking the 750 kV demonstration electricity transmission line in Guanting–Lanzhou East as an example, representative loess samples were selected for compression and collapsing sensitivity tests. Four foundation treatment schemes were designed, and the wetting deformation characteristics were investigated through numerical simulation of the rainfall infiltration process. Corresponding optimisation schemes were proposed. The collapsing process was divided into four stages through laboratory collapsing tests. The relationship function between saturation and the Duncan–Chang model parameters of loess was established, which was introduced into the finite element model to consider the rainfall infiltration process. The analysis of the displacement field, and loess saturation field with time after rainfall infiltration for the four schemes showed that adding a lime-stabilised soil cushion layer and waterproof layer to the inclined column foundation had the best effect. Given that the design scheme needs to consider safety and economy, the thickness of the cushion layer was optimised, thereby reducing the use of lime-stabilised soil by 20%. Research findings provide meaningful guidance for the design of transmission tower foundations in loess areas.