Research On Relevant Indexes Of Deformation Control And Settlement Calculation Method Of Pile Foundation

With the large-scale construction of high-speed railway,urban rail transit,Bridges and ports,high-rise buildings and underground space as well as urban infrastructure,the development of pile foundation technology is advancing by leaps and bounds.At the same time,more and more engineering requirements according to the deformation control design,the development of pile foundation engineering according to the deformation control design theory is the need of engineering construction development.In order to pursue the overall and local balance between resistance and load,realize the optimal layout of supporting stiffness and minimize the differential settlement,the idea of variable stiffness leveling has been accepted by designers gradually,but the detailed rules for the real leveling design process have not been introduced yet.Enhancing the ability of pile foundation engineering deformation calculation is the basis of further developing the theory of pile foundation engineering deformation control design.Most of the settlement calculation of pile foundation is a semi-theoretical and semi-empirical method.However,due to the lack of reasonable determination of additional stress,the calculated results differ greatly from the actual ones,and a large empirical coefficient is often needed to correct them.Therefore,it is necessary to carry out further research on the deformation control index and settlement calculation method of pile foundation.The main research contents of this paper are as follows:1.The pile raft foundation through large scale model test of the pile raft foundation in order to determine the variable stiffness leveling control settlement design key technical indicators,pile raft foundation to control settlement index,pile jacking counterforce distribution,load transfer rule by the side of pile,pile end,ratio of deformation influence depth to study the related indexes such as law and raises the level control settlement rules for quantitative analysis.2.Based on 53 test piles with complete test contents in different geological conditions and 9 engineering measurements,the settlement calculation method of pile foundation which can more accurately determine the additional stress of pile group foundation is studied.Through model test research and practical engineering case verification,the following main conclusions and results are obtained:1.The control settlement index of pile-raft foundation varies with the strengthening index under different pile diametric distances and pile distribution modes(pile number).In the range of(1<?_s<1.3),the standard settlement ratio and standard stiffness ratio have approximately linear relationship with the strengthening index,and the change rate has little influence with pile distance and pile number.2.The horizontal influence range of pile-raft foundation is about 6d,and the influence depth of vertical settlement deformation is about 1 times the pile length under the pile tip plane.The pile group effect makes the end resistance of pile raft foundation greater than that of single pile.The superposition of pile-soil stress field effect does not change the distribution of pile resistance.The reaction force of pile tip increases with the increase of load level,the Angle pile the largest,the edge pile the second,and the center pile the least.When the load level approaches the ultimate bearing capacity,the reaction force of pile top tends to be uniform.3.Four types of pile lateral resistance generalization models,namely trapezoid,conical head,garlic head and concave valley,are put forward.It is more practical than Geddes simplified model,and an empirical method is established to determine the generalized model of lateral resistance distribution comprehensively by using engineering geological data and the ratio of length to diameter of foundation pile.4.Considering the influence of pile diameter,Mindlin solution homogenizing additional stress method is proposed to calculate the settlement of pile foundation(integral homogenizing layer-sum method,layer-sum method of foundation pile and composite foundation pile)according to the lateral resistance generalization mode,and the relevant calculation software is improved.5.The reliability of the proposed calculation method is verified by 9 projects and6 large scale model tests.