Study On Settlement Of Piled Raft Foundation Considering Pile Group Effect

At present,with the vigorous development of infrastructure construction in China,especially the continuous development of high-speed railway and high-rise buildings in recent years,they put forward strict requirements for controlling the settlement and deformation of foundation,Because of its high bearing capacity,small deformation and uniform settlement,pile-raft foundation is the first choice for the lower structure of buildings,so it is widely used.Although there are a lot of research results on settlement calculation of piled raft foundation,due to many factors,there is still no accurate method to determine the settlement of piled raft foundation.In this paper,the influence of pile-soil load sharing ratio and pile group effect on pile-raft foundation is studied by numerical simulation technology,and the settlement calculation formula of pile-raft foundation is summarized and refined,which is applied to the settlement prediction of pile-raft foundation and verified by an example.The specific work is as follows:(1)The three-dimensional model of pile-raft foundation with two piles was established by ABAQUS.The load-sharing ratio of pile-raft foundation was studied.The effects of pile spacing-diameter ratio,pile length-diameter ratio and elastic modulus of soil between piles under raft on load-sharing ratio were compared and analyzed.The formula for calculating the load-sharing ratio of piles under various influencing factors is summarized and concluded.When the pile spacing-diameter ratio,length-diameter ratio,soil modulus between piles,cushion thickness and cushion elastic modulus are known,the corresponding load-sharing ratio of piles can be calculated through the formula.(2)The principle of interaction coefficient method is applied to finite element analysis,which makes up the shortcoming that the interaction coefficient method based on elastic theory is only applicable to elastic analysis.The pile-pile interaction coefficients are calculated by changing the parameters of pile spacing-diameter ratio,length-diameter ratio,pile-soil elastic modulus ratio and end-to-side modulus ratio.The empirical formula forcalculating pile-pile interaction coefficient is obtained by non-linear regression analysis.The pile-to-diameter ratio,the ratio of length to diameter,the ratio of elastic modulus of pile to soil and the ratio of end-to-side modulus can be determined by formula,and the pile-to-pile interaction coefficient can be calculated by superposition method.(3)Based on the principle of load plate experiment,the pile-pile interaction coefficient is extended to the soil-pile interaction coefficient,and the influence on the pile caused by the settlement of soil at different positions is obtained.Based on the calculation formula of soil-pile interaction coefficient and pile-pile interaction coefficient,a set of prediction flow of pile-raft foundation settlement is obtained by iteration.Through two engineering examples of pile-raft foundation,combined with the settlement prediction process of pile-raft foundation,the comparative study is reviewed.The results show that the error between the settlement calculated in this paper and the settlement recorded in the actual project is small,and the calculation process is simple and saves a lot of computer time.