Study On The Engineerining Characteristics Of Composite Foundation With Plain Concrete Combined Piles

With the rapid development of tall building,the structure and construction is increa-singly more and more complex.The demand of ground intension,settlement and difference settlement is so inflexible that the crude soft soil must be dealt with artificially.Nowadays, composite foundation is one of the most widely used ground treatment technologies. Composite foundation with plain concrete combined piles will be broad development prospects,owing to a high power effectively reduce the deformation of foundation control difference deformation and extensive adaptability and good economic benefit in the engineering construction and a large amount of application.Based on the research on Boshi gongguan in Chengdu and the composite foundation theory of plain concrete piles,the thesis innovatively puts forward the design method of composite foundation of plain concrete combined piles with different length and diameter (herein collectively referred to as composite foundation with plain concrete combined piles).On the basis of field tests and in situ monitoring of test results, the paper analyzs and discusses working properties of the composite foundation mentioned above mainly in the following aspects:(l)Simply introduce the characteristics of the composite foundation,the general situation of development and basic theory,compares bearing capacity and settlement calculations theory of this type composite foundation,make an inquiry into their advantages and disadvantages.(2)Based on the deep plate loading test, pile shaft resistance test, in situ monitoring test, soil information and ground treatment design,the thesis analyzes large-diameter plain concrete piles p-s curve of load test and the ultimate shaft resistance test, then draws the stress of the pile,stress of the top pile,pile-soil stress ratio. Conclusions:throughout the construction process,there is negative skin friction on the large and small-diameter plain concrete piles,the location of the neutral point respectively distance from the pile top2>.5m,1.5m.With the increase of the upper structure load,soil pressure of pile top,axial force and pile-soil stress ratio also increase gradually.(3)The finite element software of ANSYS10.0is used to simulate the composite foundation of plain concrete combined piles. According to comparing the measured data with the result of numerical simulation,finite element analysis precision can meet the project demands.On this basis,explore the law of settlement and pile-soil stress ratio with the increase of the upper structure load. And analyse the various factors (such as pile length, pile modulus,cushion thickness,cushion modulus) on affecting the reciprocity of the pile and soil,and the more reasonable range of the thickness of cushion and length of the pile be gained.