Research On Capping Effect Of Pile Foundation In Railway Bridge Engineering

In recent years, with the rapid development of economy in our country and rise of infrastructure construction, how to save the cost of infrastructure construction has become a more and more important topic. The Composite Pile Foundation has fully considered the influence of shared loading of soil between piles, which decreased the number of piles; therefore, it has good economic benefit and wide application prospect. In recent decades, experts at home and abroad have gain great achievements about this subject. However, the description about influencing factors for cap effect of the composite pile foundation still needs improvement, especially about the impact of cap thickness and soil strength.Based on a major scientific project of Beijing-Shanghai High-speed Railway "Research on Post-grouting Technology for Pile Foundation in Soft Soil in High-speed Railway", this thesis started from the description of the composite pile foundation theory and analyzed the influencing factors of pile capping effect. With the date collected from the site, the thesis analyzed the stress distribution characteristics of soil at the bottom of the cap and came to some conclusions with referential value to other post-grouting projects. Thereafter, with FLAC3D numerical simulation, the thesis analyzed the influence of loading level, pile distance, thickness of cap and soil strength on the shared loading of soil between piles, which will benefit the cap theory for composite pile foundation.It indicated by the site survey and the results from numerical simulation that: Stress of the soil at the bottom of composite pile cap is small in the middle while huge at the boundary; the loading level and pile distance have a major influence on shared loading of soil between piles:the higher the level is, the bigger the loading proportion of share loading is; the bigger the pile distance is, the bigger the loading proportion of share loading is. Furthermore, the thickness of cap and soil strength has an influence on shared loading of soil between piles:the thicker the cap is, the smaller the loading proportion of share loading is; the harder the soil is, the bigger the loading proportion of share loading is.