Research On Bearing Capability Of Post Grouting Pile Of Highway And Bridge In Loess Area

Post grouting pile means when pile foundation construction has been done for a certain time, Inject cement slurry through grouting pipe the pile tip preset in the pile and the connected grouting valve in the end and the side of the pile to make the soil in the end and the side of the pile(including sediment and mud) been reinforced, so that it can improve the bearing capacity of single pile and reduce the pile settlement. This technology has been widely applied in the construction, while there are few applications of the technology in pile foundation of highway and bridge, and relevant experimental research is lacking. In this paper, based on the special highway Weihe special bridge of Xi’an Xianyang International Airport, this paper carries out experimental research on the bearing capacity of the post grouting pile of the highway bridge, main research work is as follows:(1) carrying out a detailed geological survey of the experimental area, and according to the experimental purpose, in the full use of the pile foundation, developed a detailed field test program, a total of 9 test piles, divided into three groups.(2) The contrast experiment show: The rebound rate of the post grouting pile is between 86.2% and 76.7%, and the rebound rate is 16.3% to 20.9%;at the same level load, the settlement of pile foundation with the post grouting technology is reduced by 30%~80%, and the settlement curve of the post grouting pile more moderate; compared to conventional filling pile, the ultimate bearing capacity of single pile of post grouting pile with combined grouting technology is increased by more than 8000 kN, or 50 percent. It shows that post grouting technology can significantly improve the pile bearing deformation characteristics and the vertical bearing capacity.(3) When axial force of pile shaft was analyzed, it was found that axial force and numerical analysis of measured pile shaft of post grouting pile foundation of 25 meters and normal pile foundation was basically consistent. When pile side frictional resistance was analyzed, the position of maximum frictional resistance obtained by numerical simulation is generally lower than the measured results, among which, the post grouting pile foundation is particular significant. Measured maximum lateral frictional resistance position of normal pile foundation of 25 meters is 10~15 meters, maximum lateral frictional resistance is 130kPa; Measured maximum lateral frictional resistance position of post grouting pile foundation of 25 meters is 10~15 meters, maximum lateral frictional resistance is 180 kPa.(4) Settlement monitoring results in operation period show that: the pile foundation of each bridge pier of project is less than 3mm, and no significant settlement has been found. From the general trend of settlement, it can be seen that settlement of post grouting pile foundation is slightly less than the conventional bored pile foundation in operation period.