Time Efficiency Analysis And Calculation Method Of Rigid Pile Composite Foundation’s Pile-soil Stress Ratio

In recent years,the state has made great efforts to develop highway,railway and other transportation projects.Due to the project needs,engineering construction is often carried out on soft soil with poor carrying capacity,which results in the rapid development of the rigid pile composite foundation treatment technology.Compared with the ordinary rigid pile foundation,a layer of bulk material is added to the pile top plane in the rigid pile composite foundation.When the upper load is loaded,the cushion layer can adjust the deformation between the pile and soil,so that the pile and the soil will always bear the upper load,thus the bearing capacity of the foundation is raised to a greater extent.Rigid pile composite foundation can be used to deal with silty and silty clay and other soft soil foundation with poor bearing capacity and high moisture content.Compared with the soil with low water content,the consolidation settlement of soft soil foundation with high water content has very obvious time effect.After pile driving,the consolidation speed of soft soil is faster.The pile-soil stress ratio also has obvious time effect.The pile-soil stress ratio reflects the bearing condition of pile and soil composite foundation.Therefore,the research on time effect of pile-soil stress ratio of rigid pile composite foundation is of great important value to the engineering design of pile soil composite foundation in soft soil area.The paper is to study the calculation method with the time efficiency of the rigid pile composite foundation’s pile stress ratio.First,through the analysis of the bearing capacity of the pile and the drainage consolidation theory of the soil between piles,the paper studies the time effect of the pile stress and the soil stress.This paper firstly selects the single pile and the soil from its reinforced area as a calculation unit to analyze.Then,based on the load transfer method,it obtains the settlement deformation relationship among the components of the calculation unit,then it deduces the compatibility equation among the components of the rigid pile composite foundation.Afterwards,the study reasonably simplifies distribution curve of the pile-side friction to get the formula of the pile stress and the soil stress transforming with depth,which is combined with the formercompatibility equation of deformation,then deduces the formula of the pile-soil stress ratio considering the time efficiency.Then,through indoor model test,it is verified that the calculation formula of pile-soil stress ratio without considering time efficiency is feasible.In a practical project,the formula is used to calculate and analyze the bearing capacity of the composite foundation,and the relation curve of pile-soil stress ratio over time under different geological conditions is obtained.Then the finite element software ABAQUS is used to simulate the rigid pile composite foundation in the project,and the simulation results of pile-soil stress ratio change with time are compared with the calculated results.Then the feasibility of the method is verified.The research shows that there exists obvious time efficiency in the pile-soil stress ratio of the rigid pile composite foundation and cannot be neglected in calculation.This time,the efficiency presents that the pile-soil stress ratio increases with time passes,then slightly decreases and finally tends to stabilize.