Offshore wind energy will become one of the important sources of energy in the future, and root piles with good pullout bearing characteristics can be used for the foundation of offshore wind power generation facilities. Through the model test, the pullout bearing characteristics of root piles with different water content states in coral sand foundation are comparatively analyzed, and the pullout bearing deformation law and pile body force transmission characteristic law of root piles is revealed. The results show that when the coral sand foundation is saturated and the water level rises and falls, compared with the dry sand foundation, the pullout bearing capacity of the root pile decreases, and the ability to control the displacement is sharply weakened. The axial force curve at the root is in the shape of a step; after the foundation is affected by water, the maximum value of lateral friction resistance first appears at the bottom root, and the lateral friction resistance at the lower root is always greater than that at the upper root; the water level rise and fall leads to a decrease in the lateral friction resistance in the area of the pile without a root, and the lateral friction resistance in the area of the root is increased. Under saturated and water level rise and fall condition, the total bearing ratio of the root pile increases, and the bearing ratio of the lower root pile is always larger than that of the upper root. After loading, the soil in the upper part of the pile is compacted, and the soil in the lower part is loosened; the maximum value of soil pressure in the compacted area of the dry sand condition gradually moves downward, and the maximum value of soil pressure in the saturated and water level rise and fall condition is always located in the lowermost part of the compacted area; the pore water pressure in the saturated and water level rise and fall condition is basically equal with the hydrostatic pressure, and there is no obvious super pore water pressure generated. The research results provide scientific basis for the application of root piles in coral sand foundation.

Deep foundation and anchorage systems are often comprised of simple linear elements, limited by design, materials and techniques employed to build them. Their stability is attained by transferring structural loads to deeper, more stable soil layers across a larger area, reducing potential for excessive settlement and providing resistance against lateral forces from external factors including wind and earthquakes. In comparison, root systems distribute loads to a large volume of soil through a branched morphology of semiflexible elements. Roots also penetrate soil media, reduce erosion, create habitats, and exchange, store and transport resources, while continuously sensing and adapting to environmental conditions. Insights from their integration of multifunctionality can be transferred to civil engineering through biomimicry. As a first step toward designing root-inspired foundations, the effects of various morphological traits (laterals' length, number of nodes, number of laterals, branching angle and laterals' cross section) on foundation performance are evaluated through vertical pullout tests. Out of the model properties, general trends were observed, including the positive correlation between models' surface area and maximum force reached. Yet, due to complex interactions between the model and granular media, no model property fully explained differences in pullout resistance of all models. The effects of each root trait on pullout resistance were analyzed separately, which can serve to adapt the design of root-inspired foundations and exploit granular physics principles. Potential reasons for surprising and counterintuitive results are also presented. Further studies could evaluate the assumptions given as potential explanations of these results by studying identified counterintuitive scenarios.