Study On The Pile-Soil Interaction Of Bridge Pile-Group Foundation Under Active Load In Soft Soil Area

In the soft soil area, because of the characteristics of low strength and high compressibility, pile foundation is generally selected to deal with the foundation of High-speed Rail. But the bearing property of pile foundation in soft soil area is a very complicated process of pile-soil interaction under horizontal load. At the same time, M-method in the code is affected by many factors, designing for pile foundation of lateral load can not achieve expected result in soft soil area, some optimizing can be achieved. Therefore, the paper considered the foregoing deficiencies comprehensively, then analyzed the main factors(pile lengthu、pile diameter、pile spacing etc.) which affect the horizontal bearing property of both single pile and pile-group foundation, by using Finite Element Method(FEM). In addition, this paper analyzed the value of "m" by means of inversion and statistics. The main conclusions are presented as follows:1.The horizontal displacement and bending moment of pile increases with increase of the horizontal load for single pile and the pile group. For the foundation of pile group, with the change of horizontal force, the change pattern of horizontal displacement is consistent to each other, and the maximum bending moment of the front pile is larger than those of all the rest of piles, in which the maximum bending moments are same to each other generally.2.The pile stiffness has little influence on the horizontal displacement, bending moment of pile and the allocated proportion of the maximum bending moment of each row pile for both single pile and the pile-group.3.For both single pile and pile group, the horizontal displacement of pile decreases and the bending moment of pile increase with increase of pile diameter. For the foundation of group pile, increasing diameter of pile improves a bit allocated proportion of the maximum bending moment of all the piles except those in front row.4.For both single pile and the pile-group foundation, with increase of pile length, the horizontal displacement and bending moment of pile are barely changed. For the foundation of pile group, increasing length of pile can improve a bit allocated proportion of the maximum bending moment of all the piles except those in front row.5.For pile-group foundation, the increasing of longitudinal-pile space will leads to the decrease of pile horizontal displacement obviously and pile bending moment. In addition, the allocated proportion of the maximum bending moment of piles in middle and back rows decrease more(13%generally); the increasing of lateral-pile spacing causes the decrease of pile horizontal displacement, Yet an opposite trend is observed in pile bending moment., the allocated proportion of the maximum bending moment of middle and back pile decrease slightly(2%and9%generally).6. For pile-group foundation, three typical soft soil layers of Hu-Tong High-speed Rail project are selected to do the research in this paper, the maximum bending moment proportion of middle pile to the front pile is65%-74%, the maximum bending moment proportion of back pile to the front pile is55%-73%.7. The variation range of "m" as well as the relationship between "m " and parameters of the region can be gained through inversion and statistical analysis.