Research On Strengthening Mechanism And Bearing Character Of Grouting Pile Composite Foundation

Grouting pile, which introduces technology of grouting, is a new kind of composite foundation processing technique to improving soft foundation. In recently years, theoretical research of grouting pile composite foundation has been fallen behind engineering practice. Based on former research, this paper carries on analytical research on bearing character of grouting pile composite by means of theoretical analysis and finite element analysis, puts forward the calculation method of grouting pile composite foundation, analyzes changing law of pile-soil stress ratio. The main works is listed as follow:1) By studying reinforcement mechanism and character of grouting pile, the reinforcement mechanism of grouting pile is brought forwards as follow: serious fluid not only cements skeletal material to form pile, but also aggravates frictional resistance and end resistance of grouting pile. In additional, based on synthetically action of serious fluid as permeating, cementing, squeezing, there is a diffusing zone in composite foundation. Three parts as pile, diffusing zone and undisturbed soils bear jointly load.2) Studying the character, radius of serious fluid diffusing zone and influencing factor of diffusing zone's radius. Based on taking diffusing zone into account, bearing capacity formula of composite foundation is amended to adapt grouting pile composite foundation, which is validated by practice project.3) Based on the practical situation, a calculation model is generalized. By using this model, a coordination equation of pile-soil stress ratio and serious-soil stress ratio (stress ratio between serious fluid diffusing zone and undisturbed soil) is deduced with elastic theory and limiting equilibrium breaking theory under embankment. Based on the coordination, theoretical research is carried out, which is validated by engineering practice.4) By using the Plaxis FEM software, bearing character of grouting pile composite foundation is analyzed from such factors as pile-soil module ratio, serious-soil module ration(module ratio between serious fluid diffusing zone and undisturbed soil),pile replacement ratio, diffusing zone replacement ratio,capping plate replace ratio. In the course of calculation, the element of diffusing zone is added in consider the pile character.