A Time Effect Analysis Of The Settlement For Composite Foundation With Cement Fly-Ash Gravel (CFG) Piles

As an effective way of ground improvement,composite foundation has been widely used in engineering practice in recent years.However,bearing mechanism and calculation method of composite foundation has far fallen behind engineering practice.Therefore,the theoretical research for calculation of composite foundation has been one of the important fields for research and development of geotechnical engineering at present and even for a long period in the future.Accurate calculation of settlement and reasonable control of settlement in composite foundation are very important,due to the situation, the idea of design according to settlement of composite foundation was proposed,it can be more appropriate for use in composite fondation.Moreover, design according to settlement of composite foundation can guarantee the safety of buildings and save project investment.At present the theory of composite foundation on settlement is still not mature, therefore, based on the existing research results,the theory of settlement shall be constantly modified and improved, and the accuracy of foundation displacement field is enhanced.The time effect of settlement has already aroused the concern of the domestic and foreign scholars,but few things about it were reported now.Effective prediction of settlement is important to control the building's stability, only through studying the time effect of settlement can raise a higher level of calculation on settlement of composite foundation,and better develop its theory,also be helpful to promote the technique of composite foundation.As a kind of new economical and reliable technique for capacity of improving the weak ground,the CFG pile composite foundation is one of difficult points in the field of geotechnical engineering. However,in spite of being already widely applied in foundation engineering now,the theory for calculation of composite foundation has also far fallen behind engineering practice.Through three ways of theoretical derivation,measured data,numerical simulation,the time effect of settlement on the CFG pile composite foundation has been made relatively careful research.Firstly based on the theory of cavity expansion and the three dimension analytical formula of excess pore water pressure through Biot consolidation equation, a new kind of method to calculate the consolidation degree of subsoil in CFG piles composite ground is presented, and further a new kind of method that can reflect the time effect of settlement to calculate the anytime settlement of CFG piles composite ground is also presented.At the same time by using the finite element analysis software ABAQUS, the settlement characteristics of the CFG pile composite foundation has been analysed. the factors affecting the pile and pile-among soil settlement of the CFG pile composite foundation has been studied,including load level,cushion thickness,cushion module,pile and pile-among soil module, rate of eplacement,pile length and so on.These studies can play a referenced and helpful role to improve and develop calculation methods on settlement of composite foundation in the future, as well as help to promote the use of the CFG pile composite foundation.