The power construction company recognizes that China is vast and that geological conditions vary significantly from one region to another. In some areas, the soil is soft clay; transmission line foundations constructed on such soil are referred to as soft-soil foundations. Typically, three types of soft-soil foundations are used: cast-in-place bored piles, spread footings, and mat foundations.

　　Among these, spread footings are relatively simple to calculate, but they place stringent demands on earthwork excavation and reinforcement, require a large footprint, and often present logistical challenges during construction due to the difficulty of material handling, thereby significantly reducing the degree of flexible construction. Mat foundations are more expensive, involve extensive design considerations, and are complex to construct. In particular, when soft ground conditions are prevalent during construction, construction quality can be compromised, increasing construction difficulty and making it inherently harder to ensure quality. Bored pile foundations are also costly, and their construction quality is difficult to control.

　　The power construction company believes that line foundation works in different regions exhibit certain differences in construction materials, construction techniques, and methods for assessing foundation conditions. Among these, permafrost foundations account for approximately one-fifth of the national total. The underlying principle is that the mechanical properties of permafrost frequently change under freeze–thaw conditions, leading to corresponding variations in strength parameters, topographic features, and surface structures. Winter conditions are particularly prone to safety hazards; frost heave and thaw settlement are common types of such hazards in permafrost areas and are typically mitigated through structural measures. Based on local climatic characteristics and construction requirements, permafrost foundations are generally treated using drainage–impermeability methods, physicochemical methods, and soil replacement methods.

　　Power construction companies identify three common types of loess pipeline projects: excavation, rigid stepping, and excavation. In areas with thick soft soil, pile foundations are often used to penetrate the soft-soil layer for treatment. However, with rigid stepping, uneven stress distribution can occur, leading to excessive use of construction materials and higher project costs. As technology advances, this approach is readily abandoned; in contrast, the excavation-pit model has become widely adopted.

　　The power construction company believes that route selection and surveying are of paramount importance in route design. In relatively remote mountainous areas, the large number of survey stations and the varying levels of professional competence among survey personnel can lead to inconsistencies in survey accuracy, which in turn affects the precision of geological surveys for tower foundation sites. For instance, some areas are located on steep slopes where soil and water loss is widespread and landslides are frequent; therefore, it is essential to improve methods for identifying geotechnical conditions. Furthermore, based on the topography of the tower site, existing landforms should not be simply disregarded, and appropriate protective measures must be implemented.

　　The power construction company believes that, in light of the commonly used foundation types in transmission line projects today, foundations can be categorized into excavated foundations and in-situ soil foundations. Excavated foundations primarily include stepped foundations and mat foundations, while in-situ soil foundations mainly comprise excavated foundations, cast-in-place pile foundations, and rock-socketed foundations. Given the high cost of bored cast-in-place pile foundations and the stringent site conditions required for rock-socketed foundations, this paper conducts a comparative analysis of stepped foundations, mat foundations, and excavated foundations.