Behavior Description And Design Optimization Criterion Of Single Pile Force-displacement

With the rapid development of urbanization in China,piles play an important role in high-rise,super-high-rise buildings and most infrastructure construction.As a widely applicable and effective foundation,pile foundation has always been favored by the engineering community.Load-settlement of pile foundation is an important sign to check whether the pile foundation is reliable.At present,the study of load-settlement of pile is more extensive,but it is difficult to find a more effective calculation method.In this paper,three calculation methods of pile foundation load-settlement are introduced in detail: load transfer method,elastic theory method and shear displacement method.The advantages and disadvantages of these methods are compared in depth.Because the interaction between pile and soil is complex,the current theories are basically ideal elastic-plastic models.Moreover,the load transfer function of piles has always been in the research stage,and its application in engineering is still in the semi-empirical and semi-theoretical state.After introducing the traditional method,this paper introduces a new constitutive model and a method to determine the relevant parameters.The model can well reflect the interaction between pile and soil,especially the load-displacement relationship between pile and soil at pile tip,and the shear stress model of the model can well reflect the load transfer of soil at pile side.Therefore,the constitutive model is well applied to the study of pile-soil.Based on this constitutive model,a new method for calculating the load-settlement of pile top,force method and displacement method,is proposed by using linear or elastic-plastic model(this paper focuses on displacement method).By adding a section of settlement displacement to the pile bottom,a new constitutive model is used to calculate the load-settlement curve of the pile top.This method is more effective in calculating the load-settlement curve of piles in layered foundation.This paper analyses the static load test data of Changsha Bay Bridge,substitutes the test data into the new constitutive model,calculates the load-settlement curve of pile foundation combined with the new method of calculating the load-displacement settlement of pile foundation,and compares it with the curve obtained from the test,which has a good correlation.In order to further verify the correlation,this paper uses MIDAS software to simulate.The simulated curves have good correlation with the experimental and calculated curves.The validity and applicability of the new constitutive method for calculating the load-settlement of pile foundation are verified.By calculating the load-settlement of pile foundation,the design criterion of optimizing pile foundation is put forward in this paper.This optimization abandons the traditional equal section and equal strength design,and puts forward two optimization methods of equal section and equal strength and variable section,and provides the design principle,calculation method and optimization principle of these two methods.The optimization principle can select pile type safely and economically,and make more effective use of resources.