Reserch On Mechanical Characteristics Of Subgrade Pile-Plank Structure Under Horizontal Thrust

The subgrade of pile-plank structure depend on the interaction of three aspects of pile, soil and structure to form a composite structure system that can effectively control the settlement of subgrade and its upper structure and can maintaining its stability. But the theory of the pile-plank structure is still lacks, in order to further expand its design theory and engineering applications, on the one hand, this paper use ABAQUS numerical modeling approach to analyze its characteristics are affected by the level of thrust force in landslides, on the other hand select the actual operating point of its field force and deformation monitoring in order to further verify the results of the analysis and put forward some conclusions that can be used. This paper analyzes concluded the following:1.The force of embedded pile-plank structure is more reasonable than other two types through analysis the structural mechanics theoretical calculations of the three categories of embedded, pillar type and joist type pile-plank structure. However, due to the presence of the overlying graded gravel, under the case of the rest of external load are same, the force will be additional increases than other two types, so it need thicker bearing plate or the material whose parameters are stronger in the design of embedded pile-plank structure. The force of joist type pile-plank structure is relatively small, combined with the joists connect two piles into a whole, its overall performance is better and have characteristics of faster construction, less material, lower cost and conducive to large-scale in the use of this structure.2.The pile-plank structure would be inevitably affected by additional factors when the horizontal thrust, the sliding angle and the cantilever height increases, the analysis and comparison are made for the three situations through calculating the model that build by ABAQUS, and the results demonstrate:The increased horizontal thrust would intensify the downward trend of sliding body, the shear of pile foundation increases violently at the sliding face, at the same time, the maximum shear force is much larger than the original model, it suggests that the shear strength of pile near the sliding face is high demanding. So it should be paid more attentions in the engineering measures. Suggestion is raised that increase the ratio of reinforcement properly in the circumstance, if it can’t change the size of section, the displacement and bending moment of pile reaches the maximum value at the top of pile, the displacement of pile is near the limit, namely that the landslid is in critical failure state when the strength reduction coefficient reaches1.15. 3.Through monitoring the field site, the results demonstrate: there will be a pile "staggered" phenomenon, the displacement of each pile near the sliding face exist a certain mutation. Because the pile below the sliding face is embedded in stable rock, the pile above the sliding face will develop obvious deformation due to the landslide thrust; the maximum stress of pile appears in the near of the sliding face. Because only the pile above the sliding face bear the thrust force of landslide. Under the assumption of that the part below the sliding face is fixed and the pile at the sliding face is completely fixed bearing, because of the "staggered" phenomenon, the displacement of pile near the sliding face is the maximal, so its internal stress is the maximal,too.