Study On The Composite Foundation With CFG-Pile For Improving Thick And Soft Ground

Based on the idea of controlling post-construction settlement, theoretical study andengineering practice of CFG pile composite foundation for thick and soft ground treatment isintroduced combined with some main scientific and research project in this paper. The researchand achievement mainly embodied in four aspects: the field test, the laboratory model test, thetheoretical analysis and the numerical calculation.The field test research includes the following works: the engineering geological charactersof the test section are analyzed in detail and the construction technique and the design parametersof the CFG pile composite foundation are determined according to the conventional method; thequality of the CFG pile and the effect of reinforcement are analyzed according to the field testand quality test results; the settlement, the pore water pressure, the stress distribution of pile andsoil, the stress transfer mechanism and the bearing capacity of CFG composite foundation underembankment load are analyzed according to the test results.The laboratory model test research includes the following works: the design and preparationof the laboratory model according to geometrically similarity criterion; the simulation of theprocess that forming the piles and analysis of the soil-squeezing effects; The behaviors of thedifferent length and space model piles such as the deformation, the bearing capacity, the stressdistribution and the stress transfer mechanism are studied through stress-deformation test andload test, especially for the partially penetrated CFG piles.The theoretical analysis and the numerical calculation includes the following works: thestudy of the increment and dissipation of the excess pore water pressure based on the theory ofcavity expansion and relative field test results, the establishment of the analytical consolidationtheory of the early setting period of the CFG piles based on the axisymmetric sand drainconsolidation theory considering of the changing of the permeability, the calculation of theincrement and dissipation of the excess pore water pressure of soil in early setting period, theestimation of the soil compaction displacement and ground bulging in the period of constructionof CFG piles based on the existing method; the derivation and establishment of the analyticalconsolidation theory of CFG pile composite foundation in different conditions under the load ofembankment based on one-dimensional consolidation theory and double-layered groundconsolidation theory; the numerical simulation and verification based on plane finite elementanalysis of pile groups; the study of the load transfer and deformation in different designparameters of CFG pile composite foundation under the load of embankment based on theanalysis of finite element method; the research and verification of the design calculation methodof controlling post-construction settlement of CFG pile composite foundation based on the ideaof the post-construction settlement is composed of the unfinished primary consolidationsettlement of the reinforced field, the unfinished primary consolidation settlement of underlyingfield and the secondly consolidation settlement of the reinforced and underlying field.