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CFG pile is short for the cement fly-ash gravel pile,which is mixed to a high bond strength pile with sand and water.CFG pile composite is formed by CFG pile,the soil between piles and cushion. It is developed as a new foundation reinforcement technology at late 80s of the 20th century. Because of its advantages such as timber economy, construction shortcut and good strengthening effects,it has been widely used in the construction.In the first chapter,the background and the innovative points are introduced first. Theoretical basis of CFG pile-raft structure is studyed mainly,and bearing capacity,deformation,pile-soil stress ratio,transfer law of loads, cushion effect and other research results about the CFG pile composite foundation are studyed mainly too.In the seconded chapter,based on the field tests of the CFG pile composite ground under the flexible foundation of high speed railway, the paper introduces the condition of the field test in detail and lists the main test results first.Then the test results of the pile-soil stress, the deep soil pressure, stress and strain of the pile and sedimentation are analyzed.At last the law of reciprocity of the pile and soil of the soft soil ground treated by pile-raft structure are obtained,which validates and enriches current theory of the CFG pile composite ground.In the third chapter,the finite element software of Plaxis is used to simulate the composite ground of pile-plank structure.By contractting with the measured data,correctness and rationality are proved.Based on this, comparative analysis of various factors affectting the reciprocity of the pile and soil is made.,such as pile spacing,cushion thickness, pile length and the concrete plate height,and the law of reciprocity of the pile and soil are obtained.
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