Study On Work Mechanics And Optimization Design Of Gravel Pile Composite Foundation

With the rapid development of civil engineering construction, gravel pile composite foundation has been widely used to treat the soft soil. Because of complexity of geological conditions and gravel pile composite foundation itself, now it has been discussing and studying gradually. So combining with the item "study and application on soft subgrade treatment in freeway", it studies deeply the work mechanics and optimization design of gravel pile composite foundation through theory analysis model test and numerical simulation.Firstly, using the theory of round-hole expansion to describe the act between gravel pile and soil regarded as the plane axially symmetric problem, the calculation formula of pile-soil stress ratio and bearing capacity of gravel pile composite foundation can be got in two different conditions, considering the expansion influence area. Secondly based on the research of model test before and similarity theory, similarity rules of the model test of gravel pile composite foundation is deduced by use of dimension analytical method and a set of large-scale laboratory model experiment of gravel pile composite foundation is designed and accomplished, some useful experimental data are obtained, and from which, the relationship of pore water pressure with load and pile-soil stress ratio with time are gained. Moreover, work mechanics of gravel pile composite foundation is studied. Thirdly combining with soft soil treatment in Linchang freeway, the work mechanics and influence factors of pile-soil stress ratio of gravel pile composite foundation under the subgrade are analyzed deeply by FLAC analysis program, the stress in the consolidated area by gravel pile can be got and the primary factors of pile-soil stress ratio are pointed out in order to guide the design of gravel pile composite foundation. Last, design theory of gravel pile composite foundation by control of bottom displacement is suggested, and through a practice, the process of calculation is introduced, therefore the applicability in engineering is proved.