The complex and varied terrain of mountainous areas, with its significant undulations and diverse geological conditions, presents numerous challenges to the rational layout of transmission line towers. To effectively reduce construction difficulty, comprehensive consideration is needed from multiple aspects, including route selection, tower design, foundation treatment, selection of turning points and river crossings, and optimization of construction measures.
Route selection is the primary step in the layout of transmission line towers in mountainous areas. Steep slopes, cliffs, landslides, rock piles, landslide gullies, and other unstable areas should be avoided as much as possible. These areas have poor geological conditions and are prone to geological disasters, threatening the safety and stability of the transmission line towers. Furthermore, mountain rivers are often intermittent, with high flow velocities and strong scouring forces during flash floods. The transmission line should avoid passing near flash flood mouths and debris flows, and should be far from dry riverbeds in mountain gullies to prevent erosion. If passage is unavoidable, the tower location should be above the highest flood level to avoid erosion. In addition, special areas such as mining areas and downstream of reservoir outlets should be avoided to minimize the impact of external factors on the transmission line towers.
Tower design must be closely integrated with the characteristics of the mountainous terrain. In mountainous areas, towers with an all-around long-short leg structure should be prioritized. This type of tower can adjust the length of each leg according to different terrain slopes, ensuring stability even on uneven ground, reducing excavation during construction, and lowering construction difficulty. For areas with excessively narrow corridors, towers with vertical or triangular conductor arrangements can be selected, while considering the use of Y-type, V-type, and L-type insulator strings to minimize the width of the transmission corridor and adapt to narrow terrain conditions.
Foundation treatment is crucial to ensuring the stability of transmission line towers in mountainous areas. Mountainous areas have complex geological conditions, and tower foundations may be built on slopes or in karst areas. When selecting a slope for tower foundation construction, thorough geological surveys should be conducted to choose areas with good geology and stable foundations, avoiding areas with steep slopes and loose soil. For karst areas, the depth and width of the karst development must be fully understood before foundation design. During construction, drainage during excavation and concrete pouring must be strictly controlled to prevent rainwater and surface water from eroding the foundation surface. If the foundation is located on a slope, the distance between the slope and the center of the foundation must be strictly measured to ensure it meets engineering design standards.
The selection of turning points and river crossing points is also crucial. Turning points should be chosen in open, flat areas whenever possible. Besides considering requirements for guy wire layout and foundation stability, the necessary site area and accessibility for construction machinery should also be considered when the corner tower serves as an anchor tower or tensioning tower during tensioning. Turning points in mountainous areas can be located in lower valleys so that the tower can also be used as a tension tower during uplift. River crossing points should be chosen where the river is narrowest, the channel is straight, the banks are stable and unaffected by floods, and the geological conditions on both banks are good. They should also be as close as possible to ferries and highway bridges to facilitate access for construction and maintenance personnel.
Optimizing construction measures can further reduce the construction difficulty of transmission line towers in mountainous areas. In engineering surveying, different colors can be used to distinguish center stakes and direction stakes. The center stakes and direction stakes should be marked according to the surrounding terrain, features, and buildings to ensure the rationality and feasibility of the stake locations. At the same time, modern technological equipment and instruments, such as GPS satellite positioning surveying instruments and total stations, should be used as much as possible to improve measurement efficiency and accuracy. Regarding material transportation, for high-altitude mountainous areas without roads, mountain cableway transportation can be used, leveraging the terrain and pulleys to solve the problem of transporting materials uphill.
