Study On The Bearing Behavior Of CFG-Pilecomposite Foundation For High-Speed Railway

Foundation treatment is quite an active research domain in Civil Engineering at present. In the research and application of pile-network subgrade for high-speed railway, CFG-pile composite foundation has gained a remarkable achievement. But the related research started relatively late, and there is still a lot of work to do to improve the theoretical analysis and engineering application. In different sorts of composite foundation, the varied arrangement of the reinforcement materials and designed intensity results in different mechanism, and the calculation methods of bearing capacity and settlement differ accordingly.This paper gives a systematic research on the bearing capacity and design method of CFG-pile composite foundation for high-speed railway.First, this paper carried on a discussion on present application situation of composite foundation, gave a thorough analysis on the concept, composition, classification and action mechanism of CFG-pile. This paper also made a systematically description about the application theory of CFG-pile composite foundation used in pile-network subgrade for high-speed railway, and then had a discussion on the distinctions between reinforced cushion and the mattress layer of ordinary composite foundation. The calculation theories about CFG bearing capacity design and settlement design has been elaborated in detail. This paper also deeply analyzed the calculation of settlement resistance after construction in pile-network subgrade engineering in high-speed railway.Second, based on 6 meters-high embankment and 7 sorts of pile spacing, taking nonlinear characteristics of all kinds of composite foundation material into consideration, this paper has made a numerical simulation analysis on the settlement characteristics of CFG-pile composite foundation using numerical simulation software FLAC 3D, by this some rules of stress field, displacement field and deformation properties of CFG have been searched out. This study emphasized on the relationship between settlement and pile spacing of CFG. On the basis of this, the numerical simulation software FLAC 3D was also adopted for optimization.Last, combined with the typical CFG-pile composite foundations in high-speed railway, this paper made a discussion on the design method and construction technology about CFG Via static load test on single pile (including several experimental observations such as lateral displacement in deep layer of foundation, intensity of CFG-pile, foundation settlement, etc.) the change law of axial force of pile shaft and foundation settlement with filling load and time has been obtained. From the static load test on single pile, the Q-s relationship of composite foundation has been reckoned for the first time. Following that a comparative analysis with numerical simulation result has been made to improve the bearing behavior of the CFG-pile composite foundation in the high-speed railway.