Study On Settlement Calculation Methods Of Gravel Pile Composite Foundation Under Flexible Base

Owing to its effective usage of bearing capacity of foundation,with the advantages of high-speed construction and low cost,gravel pile composite foundation has been widely used in soft soil treatment.However,due to complexity of its bearing and deformation characteristics,the theoretical study has not been mature,remain to be further discussed and studied.At present,most theoretical calculations of gravel pile foundation are based on equal strain assumption.The impact of pile side friction on force-deformation of composite foundation is neglected and the impact of radial bulge deformation on bearing deformation characteristics is also out of consideration.Therefore,this paper intensively discusses bearing mechanism and optimized design theory of the composite foundation from three aspects,namely theoretical analysis,laboratory model experiments and numeral simulation.At first,this paper analyzes reinforcement mechanism of the foundation and summarizes its failure mode.On that basis,this paper goes into gravel pile composite foundation's common deformation mechanism and load transfer mechanism under flexible base.And it also briefly sums up analytic methods of compression deformation at present.Under flexible foundation,because of shearing strength on cross section caused by uneven bulge,analyzing composite foundation within the single equivalent reinforcement range,the paper presents the research strategy of settlement calculation which takes shearing strength of pile body's cross section into consideration.Secondly,based on analyzing reinforcement and bearing deformation mechanism of composite foundation,this paper divides the foundation into several parts,taking uneven bulge of each unit into consideration.On this basis,the paper obtains distributions of shearing strength of cross section of bulge part.Then,frictional resistance of pile-soil interface is considered.Combining reciprocal theory of shearing strength,this paper works out load transfer model of gravel pile.Afterwards,according to Hooke's law,it establishes governing differential equation of bulge deformation of gravel pile under flexible base,and it obtains soil stress ratio of composite foundation and settlement calculation methods on that condition.Moreover,the calculation procedure and design steps are provided.In addition,via specific examples,the calculation procedures are explained in detail,and its engineer applicability is verified.It provides a new thought for load transfer and deformation analysis of gravel pile composite foundation.At last,in order to further study bearing deformation of gravel pile composite foundation under flexible base,bonding with engineer practice,taking advantage of numeral analysis program of finite element,this paper gets stress distribution and displacement of reinforce area in gravel pile composite foundation.It also makes an in-depth explanation of several main influence factors of pile-soil stress ratio,and it points out its several major influence factors.Meanwhile,it designs and completes a set of relatively large size laboratory model experiment.According to experimental data,change relations of load displacement of the foundation are received,and then this paper deeply discusses bearing deformation mechanism of gravel pile composite foundation.