Bearing Characteristics And Intelligent Optimization Design Of Bonding Material Pile Composite Foundation In Shore Soft Soil Area

In the construction process of highways and railways, it is unavoidable to encounter a lot of shore soft soil grounds for crossing soft soil areas such as valleys, depressions, rivers, lakes and marshes, which show the significant differences of engineering properties, poor uniformity and complex causes conditions, but the most remarkable characteristic is that shore soft soil ground under a shallow buried inclined hard soil layer. Currently many domestic and foreign scholars have done a lot of researches aimed at shore soft soil ground with horizontal hard soil layer, but the researches of shore soft soil ground with inclined hard soil layer are less well established on the subject of theoretical research, numerical analysis and optimization design.Firstly, according to the load transfer characteristic of the composite foundation reinforced by bonding material pile with cap under the application of high embankment loads, the combination of pile with cap and a part of soil underlying pile cap are idealized as a composite pile. By supposing the displacement modes of soil between composite pile, and considering the layered property of soil between pile caps and soil arching effect of high embankment, a load transfer model accounting for high embankment- composite pile-soil intercoupling is set up in line with the principle of deformation compatibility. The formulas that for computing pile-soil stress ratio and the differential settlement between pile and soil are derived respectively, and the affect of interrelated factors such as the length of pile, compression modules of soil between piles and the dimenson of pile cap on pile-soil stress ratio is analyzed simultaneously. At last, the effect of increasing the effective diameter of the pile is characterized by the influence coefficient of the composite pile diameter λ, and the result shows that when the λ is 0.85 to 1, the calculated pile-soil stress ratio is the closest to the actual.Secondly, in order to study the bearing and deformation mechanism of flexible pile composite foundation with inclined hard soil layer,by designing the experimental plan in this paper based on uniform design principle, and use finite element software ABAQUS for numerical simulation, to obtain the bearing mechanism and settlement characteristics of the flexible pile composite foundation in the shore soft soil area with inclined hard soil layer. And then making the regression analysis and variance analysis of the experiment results,structuring the regression equations that for computing the maximum differential settlement and the maximum settlement of soil on the top surface of embankment and the top surface of foundation. At the same time, the credibility of the regression equations are tested through variance analysis table. In addition, the analysis of the settlement of pile top shows that the minimum settlement occurs on the thin side of soft soil layer.Finally, by introducing the particle swarm optimization(PSO) algorithm to the optimization design of flexible pile composite foundation and improving the standard PSO algorithm that combined the natural selection mechanism with the basic PSO algorithm,the PSO algorithm based on natural selection is obtained, from which the improved particle swarm intelligent optimization design method of flexible pile composite foundation is proposed. Meanwhile, designing variables which are based on the number of the cement soil mixing pile and the cement mixing ratio, analyzing and determining the corresponding constraint conditions, a cement soil mixing pile composite foundation optimization design mathematical model is built. At last, the total cost of the cement soil mixing pile as an objective function is optimized.