DISCUSSION ON CALCULATION THEORIES AND PARAMETERS INFLUENCE ANALYSIS OF PILE-RAFT FOUNDATION IN HIGH-SPEED RAILWAY SUBGRADE

Pile-raft foundation is introduced to treat the quaternary deep strata with high filling in Suzhou station of Beijing-Shanghai High-speed Railway. Nowadays, pile-raft foundations have been applied in foundation treatment in different areas but without any standard design methods and even no research. A calculation theory for subgrade pile-raft foundation based on Beijing-Shanghai high-speed railway is being discussed here, taking load forms and high-standard settlement control of high-speed railway subgrade into account. Two-dimension equivalent-frame method and three-dimension frame method are suggested to analyze pile-raft foundations in high-speed railway. There are some differences between the calculation results of the two methods to analyze foundations in Beijing-Shanghai High-speed Railway sites. It is advised to make a correction of the calculation results when using two dimension equivalent-frame method. The influence of some important parameters on the foundation is analyzed. It can be observed that the internal forces of the foundation will become bigger because of the weakened supporting action of soils under the raft and the weakened supporting action of pile side soil has greater effect on piles than on the raft.