Study On Analytic Method For Deformation Properties Of Long-Short Piles Composite Foundation

Along with the fast development of modern social economy in our country, the civil engineering construction development has become quicker and quicker at recent years, and the construction scale expanded day by day, its difficulty also enhanced correspondingly. At the same time, a higher request to the ground condition has been set. Especially because our country vast in territory, the foundation soil classification is complex, thus the civil engineers have met more and more questions of grounds. Ground question processing is appropriate or not, is the important matter of the insecurity of constructs as well as the national economy and the people's livelihood.Now days, the construction engineering of our country proposed a new method that combine long piles and short piles, uses the short piles to reinforce the weak soil under the foundation and enforce the bearing capacity of the surface layer soil, and can eliminate the differential settlement which causes by the partial weak soil; And the long pile falls on the higher intensity, smaller compression soil layer, so the load through the pile body to the deep ground, to the aim of enhances the bearing capacity and the control displacement of the foundation. So is the main research body of the compound foundation for long piles and short piles in this thesis.This thesis mainly aims at the long-short piles foundation in composite foundation, through summarizes of predecessor's research results and consults materials, the main contents and conclusions as followings:(1) Studies the functions of each part in the long-short piles composite foundation that the long piles, the short piles, the soil between piles and the cushion as well as the influence to the deformation properties.(2) Using the analytic method to study the bearing capacity and the settlement of long-short piles foundation. Especially the analysis of pile-soil stress ratio and composite modulus, and analyze its contribution to the formula of bearing capacity and the formula of settlement.(3) Analysis the bearing capacity and settlement of some specifically project example with analytic method which showed in this thesis, and contract with the result of numerical analysis method, some useful conclusions is made, can provide the reference for the later further research and the actual design.