Study On The Application Technology Of Screw Pile And Cement Mixing Pile In Soft Soil Foundation Of Inner Mongolia-jiangxi Heavy Railway

Composite foundation is one of the most widely used foundation treatment methods.Through the composite foundation,it can improve the bearing capacity,reduce the settlement and eliminate the liquefaction.When the engineering geological conditions are complex,and the requirements of the building's foundation are relatively high since it's own characteristics,composite piles are used in foundation treatment in more and more projects.Based on a soft soil foundation treatment project of Inner Mongolia-Jiangxi Railway and considering its stratum property,the composite pile of variable cross-section squeezed screw pile and cement mixing pile are used to deal with the soft soil foundation,the main work has been done in the following aspects:(1)The current development and development trend of composite pile type are discussed,and the common combined pile types in the engineering construction are summarized.The applicability,advantages and disadvantages of the variable cross-section screw pile used in this paper are discussed in detail.(2)Considering the structural characteristics of the variable cross-section extruded threaded pile,the main factors affecting the bearing mechanism of the pile are determined,the simplified models are established,and the related analytical expressions of the bearing capacity and the foundation settlement of the single pile are derived.(3)Based on a soft soil foundation of Inner Mongolia-Jiangxi Railway,two kinds of treatment methods are puts forward,these are the cross arrangement and separate arrangement of the screw pile and the cement mixing pile,respectively;Numerical simulation is carried out by FLAC3 D,considering the influence of two treatments on soil displacement and safety factor,the optimal way for the foundation treatment is determined.(4)The test section is set up in the field to verify the reinforcement effect of the foundation treatment method used in this paper.The rationality of the scheme is explained from the bearing capacity of single pile,the bearing capacity of composite foundation and the settlement of Subgrade in the process of subgrade filling.