The adaptability of photovoltaic steel structure foundation construction to geological conditions is a core element in ensuring the long-term stable operation of photovoltaic systems. Its design must select targeted solutions based on different geological characteristics to cope with the complex and ever-changing underground environment. In soft soil foundations, the loose soil and low bearing capacity easily lead to foundation settlement. In this case, pile foundations, such as helical piles or steel pipe piles, are required to transfer loads by penetrating deep into the stable soil layer. For example, in coastal mudflats or backfilled areas, helical piles can utilize their threaded structure to tightly interlock with the soil, enhancing pull-out resistance; while steel pipe piles increase pile stiffness through concrete pouring, adapting to lateral pressure in soft soil. If geological conditions permit, precast concrete piles can also be used, as their factory production characteristics ensure uniform pile quality and reduce on-site construction errors.
For hard rock strata or gravelly soil, the high geological hardness and difficulty of excavation require foundation construction with efficient penetration capabilities. In this case, cast-in-place piles become the preferred solution, as their mechanized drilling process can penetrate the hard surface layer and reach the stable bearing layer. In mountainous photovoltaic projects, the flexibility of cast-in-place piles is particularly prominent. The pile length can be adjusted to adapt to undulating terrain, avoiding the ecological damage caused by large-scale site leveling. If the rock strata are severely weathered or fissured, fresh bedrock must be embedded at the pile tip, and the end bearing capacity must be enhanced by increasing the pile diameter to prevent tilting risks due to uneven geological conditions. Furthermore, steel piles in steel pile foundations can also be used in rock strata construction. Their high strength characteristics can reduce the number of piles, but the steel surface needs anti-corrosion treatment to resist corrosive substances in groundwater or soil.
In collapsible loess or expansive soil areas, the water absorption and expansion and water loss shrinkage characteristics of the geology easily cause foundation deformation, requiring special design to suppress uneven settlement. Independent foundations or strip foundations in spread foundations are widely used in such geological conditions. Their large base area design can distribute the load and reduce base pressure. During the construction of photovoltaic steel structures, the base needs to be compacted to increase soil density and reduce the risk of collapse. If geological conditions are complex, a composite structure can be formed by combining pile foundations, for example, adding short piles under independent foundations, enhancing overall stability through the interaction of piles and soil. Simultaneously, a drainage system is required to divert groundwater and prevent foundation uplift or subsidence due to water level changes.
The geological challenges in permafrost regions primarily stem from seasonal freeze-thaw cycles. Repeated frost heave and thawing of the soil can damage the foundation structure. Deep foundations, such as long helical piles or bored piles, are necessary in these areas, extending the pile tips below the frost line to stabilize the soil and prevent the throttling effect of frost heave on the foundation. An insulation layer should be installed on the foundation surface to reduce heat transfer and slow the rate of permafrost thawing. Furthermore, the connection points between the foundation and the support structure must be reinforced with anti-loosening designs to prevent bolt loosening or component deformation due to frost heave.
In sandy or silty soils, the loose soil particles and low shear strength easily lead to foundation lateral displacement or overturning. In these areas, increasing the foundation depth or adding diaphragm walls enhances anti-sliding capabilities. For example, in desert photovoltaic projects, a combined foundation of helical piles and concrete caps can be used. The helical piles provide pull-out resistance, while the concrete caps resist horizontal loads through their own weight. If the risk of soil liquefaction is high, the soil surrounding the foundation needs to be reinforced, such as through vibro-compaction stone piles or high-pressure jet grouting, to improve soil density and seismic resistance.
For special geological conditions such as karst topography or mining subsidence areas, potential risks must be identified through detailed geological surveys. In karst areas, caves or underground rivers must be avoided, and the foundation location should be selected on intact rock strata. Grouting should be used to fill dissolution cracks to enhance the overall integrity of the foundation. In mining subsidence areas, the risk of ground subsidence needs to be assessed, and adjustable foundation types, such as liftable supports or elastic support structures, should be adopted to adapt to geological deformation.
The geological adaptability of photovoltaic steel structure foundation construction reflects the core principle of "adapting to local conditions." From soft soil to rock strata, from collapsible soil to frozen soil, each geological condition requires comprehensive optimization of foundation type, construction technology, and material selection to achieve stable load-bearing capacity. This adaptability is not only related to the power generation efficiency and service life of the photovoltaic system, but also crucial for ensuring structural safety and reducing operation and maintenance costs.
