Study On Settlement And Optimum Design On Composite Foundations With Different Column Stiffness

As the extensive of projects,there were more and more kinds of composite foundations.Some project such as high speed railway make high requirement for the total and differential settlements.Therefore,it is meaningful to study the rule of the deformation of composite foundation and to obtain the optimum design method.As the urbanization is speeding up,there are increasing projects in the soft soil area.It has become a top priority for architects to prevent distortion caused by the soft soil.To solve this problem,foundations are used to strengthen the constructions in the soft soil area.Composite foundations are particularly popular as a research object due to its advantage in the magnitude of the reinforcement,the speed of construction,and the prevention of distortion.Along with the wider applications,there are rising types of composite foundations as well.Therefore,it is technologically important to research the settlement pattern of the composite foundations when strengthening the soft soil foundations.Furthermore,this pattern can be used to find the optimal designs.This paper further analyzes the settlement pattern of the composite foundations based on the existing studies.The structure of this paper is listed as follows:1.With the reference of the actual projects of the composite foundations,the paper introduces the design procedures and construction process of the composite foundations,and makes a comparison of the estimates and the actual measurement of the settlement.It turns out that composite modulus method and stress correction method both overestimate the total vertical settlement of the composite foundations.Meanwhile,these two estimation methods can only estimate the total settlcement,but cannot estimate the settlement in various depths or the differential settlement.Therefore,numerical simulation is used to conduct further analysis.2.The finite difference model is used to simulate the settlement of the composite foundations.The comparison with the actual results indicates that the numerical simulation method has better accuracy than the conventional estimation methods.Thus,the model is validated.The analysis shows that the stress ratio is not a fixed value.Instead as the depth increases,the stress ratio first increases and then decreases.The treatment to the pile and the soil as a whole in composite modulus method and stress correction method is not precise.Through comparing different types of composite foundations,the most fitted pile is selected for this study.3.This paper quantitatively analyzes the characteristics of the pile,the soil and the load intensity,which may affect the design of the composite foundations.Specific influences of each parameter are discussed,and the according solutions are also pointed out.4.Simulations are conducted to research the common techniques to prevent the distortion of the composite foundations,including cushion,geogrid,grouting and non-uniform pile.The existing estimation methods do not take into consideration of the effects of these techniques,whereas they all have certain influence on the settlement and the differential settlement of the composite foundation,depending on the type of the pile.The optimal consolidation method for different types of piles is inferred,which provides valuable guidance for the construction design.