The Application Research Of Combined Pile With Gravel Pile And CFG Pile In The Soft Ground Treatment Of Expressway

Along with the rapid development of China economic and the advance by leaps and bounds of the highway construction, the problem of the soft ground treatment becomes the key factor in highway construction day by day. Therefore, it is of great significance to treat the soft ground fast and effectively in practical engineering.Based on the highway characteristics, the common soft ground treatment methods and the combination of these methods were summarized along with the advantages and dis advantages of them analyzed. Then, the mechanism, the calculation of bearing capacity, the settlement prediction and the parameter choose of gravel and CFG pile were discussed in detail. In view of the fact that the gravel pile could enhance bearing capacity and CFG pile is insufficient in draining off the underground water, in this paper, a new kind of composite ground, gracel-CFG composite ground, was proposed. And such composite ground, as a semi-rigid one, is the combination of gravel pile, CFG pile, soil and the base cushion, which could make the most of the bearing capacity of CFG pile, the underground water draining off capacity of gravel pile to avoid shortcomings of each pile and turn the soil loads into the treatment system so as to enhance the soil strength mostly. In view of the gravel pile and the CFG pile, the twice design method of composite ground was discussed and such methods as bearing testing, standard penetration testing and after-construction settlement monitoring were used to detect the treatment effect. Besides, a full series of soft ground treatment were developed including calculation, design, construction and detection system of combined pile composite ground.Finally, the proposed method was applied in an actual engineering. The section from K0+140 to K0+240 of a stretch of Nanning airport expressway in city section has soft ground and it is treated with the composite ground combined with gravel and CFG piles. The detection results show that the design requirements and the embankment standard were satisfied, which shows that such method is economical and easy to apply in practice and has wide perspective.