Experiment And Study Of Composite Foundation With Long-short Piles To Improve Deep Soft Soils Under Embankment Load

Composite foundation technique has been widely applied in soft-soil area, where theproblem of building settlement sinkage has not been solved well, especially the high-gradehighway whose post-construction settlement needs a few years to be over. So thephenomenon of bridgehead vehicle jump appears, which is a long-term technique problem ingeotechnical engineering. This paper has discussed composite foundation with long-shortpiles technology which is based on the theory of settlement control. Composite foundationwith long-short piles technology is just a attempt to deal with the problem of bridgeheadvehicle jump and the main research work is as follows:1,Rely on the experimental segment of expressway of the south shore connecting line ofHangzhou Bay Spanning Bridge, field experiment of composite foundation withlong-short-pile technology has been done and the test result has been systematicallysummarized and analyzed in which settlement characteristic, pore water pressure dissipatingcharacteristic, deep horizontal displacement characteristic and stress ratio of pile to soil havebeen thoroughly studied and some applicable conclusions also have been obtained.2,Settlement control means to change additional stress of the gound. In the test, theadditional stress of composite foundation with long-short piles has been calculated by MindlinSolutions and Boussinesq Solutions in elastic mechanics and then the settlement of the pileshas been calculated by layer wise summation method.3,Basing on the single-pile analytical approach such as load-transfer method and sheardisplacement method, on the application of group piles analysis theory and the studies ofMylonakis and Gazetas, adopting equivalent soil-pile method, considering pile-soilinteraction of composite foundation with long-short piles, the settlement of the compositefoundation has been theoretically analyzed.4,Building up corresponding body model and through numerical simulation, variousinfluential factors such as pile length, pile interval, pile end bearing layer which mayinfluence the stress and deformation behaviors of the composite foundation in the soft soilhave been studied. What's more, how the composite foundation with long-short pilestechnology controls the settlement of deep and soft soil foundation in different conditions hasalso been studied from the prospective of numerical experiment. technology controls the settlement of deep and soft soil foundation in different conditions hasalso been studied from the prospective of numerical experiment.5,According to the result of theoretical analysis and experimental study, the theory ofthe design of composite foundation with long-short piles in the deep and thick soft soilfoundation has been studied and the detail procedures of design and application have alsobeen put forward. What's more, how to design composite foundation with long-short piles inview of optimization has also been analyzed.