Centrifuge Model Tests And Bearing Charaeteristic Study Of Satruated Loess Sie CFG Pile Composite Foundation

West crude oil pipeline project is another important construction project following the West-East natural gas transmission project at the beginning of the twenty-first century, and landmark of the western development strategy. The oil tank groups in Lanzhou as the end of west crude oil pipeline bear storing,transferring to the upstream oil and providing crude oil to Lanzhou Petrochemical company. This paper serves 15×104m3 large oil tanks as engineering background and the bearing characteristic of CFG pile composite foundation on saturated loess as the research object, carried out geotechnical centrifuge model tests of the saturated loess foundation before and after the treatment and numerical simulation analysis. the test study and theoretical study of CFG pile composite foundation dealing with saturated loess are introduced systematically.The oil tank groups in Lanzhou are large oil storage facilities constructed on the saturated loess and the demand on the soil is higher. Since saturated loess is a low strength, high compression loess and the engineering properties is poor, the CFG method is used in the foundation treatment. CFG pile is improved and developed for the lack of gravel pile bearing capacity, mixing amount of stone chips, fly ash and cement to the body in the rubble pile, the bond strength of the pile is high and the pile has some characters of rigid pile and semi-rigid, The capacity of composite foundation is greatly increased. The technical issues of CFG pile composite foundation on the saturated loess are construction technology, bearing capacity of composite foundation and settlement characteristics.The bearing capacity eigenvalues of CFG pile and composite foundation are determined through on-site test. The geotechnical centrifuge model test of CFG pile composite foundation is carried out by means of geotechnical centrifuge test. The geotechnical centrifugal model test is to place the model made by prototype material according to a certain of scale in the high centrifugal force field generated by centrifuge. The stress level of the model soil is same with the stress level of the prototype, the similar deformation and failure process is shown by increasing the weight or volume of the modle. Using centrifugal modeling test, progressive settlement of the whole process of the foundation is reproduced. The settlement mechanism of saturated loess is analyzed and the bearing behavior of CFG pile composite foundation is studied.The finite element analysis model of the on-site test is established by finite element soft ware Midas/GTS. The numerical analysis of the bearing behavior and failure mode under the oil tank foundation is carried out. Provide a theoretical basis for optimal design; and the results of on-site test,model tests and numerical simulation are analyzed and compared. Learned through the work the total settlement of the foundation is smaller after adopted CFG pile composite foundation and the saturated loess foundation settlement is reduced significantly. The bearing capacity eigenvalues of saturated loess is 60kPa, and it belongs to soft ground; CFG pile composite foundation bearing capacity eigenvalues is 275kPa. Within the pile length CFG piles can fully play its friction and end resistance and substantially increase the foundation stiffness and bearing capacity of reinforced soil layers. The results verify with large oil tank saturated loess foundation treated with the CFG pile composite foundation is feasible and effective.