Ballasted Track High-speed Rail Cfg Pile - Raft Composite Foundation Settlement Calculations

To meet the extreme strict limits of post-construction settlement in Ballastless Track for High-Speed Railway, during the construction of Beijing-Shanghai high-speed railway, CFG pile composite foundation had become the most important foundation approach, and developed into the pile- raft composite foundation. Pile - raft composite foundation in high-speed railway roadbed has been still in its initial application and exploration phase, therefore, it will possess important theory and application value in researches of the bearing mechanism and settlement analysis.This article relies on the tasks of railway technology projects about "High Speed Railway Foundation and Subgrade Reinforcement Research and Technology ", combined with field survey, calculation and other means to focus on the dissipation law in settlement and pore pressure,the calculation of the total settlement and the post-construction settlement of CFG pile - raft composite foundation, the main work and conclusions are as follows:(1) Based on the field experiment of Zhenjiang section researched the dissipation law in settlement and pore pressure of CFG pile - raft composite foundation.(2)According to the settlement calculation methods of conventional pile foundation, composite pile foundation, composite foundation,the author made the computation,comparison and analysis on the final settlement of the pile-raft composite foundation, proposed a applicable combined method that include the simplified analytical solution and the Geddes method, and produced the MATLAB graphical interface operating procedure.(3) On the basis of Terzaghi one-dimensional consolidation theory, proposed the concept of influence coefficient about consolidation coefficient of CFG pile composite foundation, updated the calculation of consolidation, presented the formula for post-construction settlement and calculation steps for the allowable construction period, and validated the rationality of the method through the project case. (4) The calculation results show that it is effective of CFG pile - raft composite foundation to control the settlement, it can meet the limits of post-construction settlement in ballastless track for high-speed railway when used in the treatment of medium compressibility soil.