The Research On The Optimization Design Of Long-and-Short-Piles Composite Foundation

Composite foundation is a effective treatment method of soft ground, of the composite foundation, long-short-pile composite foundation can excavate the potential of the ground layer and availably increase foundation bearing capacity and control its settlement, so geotechnical circles have paid close attention to the long-short-pile composite foundation. Although long-short-pile composite foundation has been widely applied in engineering, its mechanical property and deformation characteristic, also its design and calculation method are still awaiting for more discuss, especially the stress and deformation rule, bearing capacity, settlement calculation method and optimization design theory of the long-short-pile composite foundation. The major research findings and conclusion of the paper is showed as follows:(1) Based on deeply analyze the calculation method of existing various kinds of pile composite foundation bearing capacity, by means of abstracting and improving, the calculation method of long-short-pile composite foundation has been gained.(2) On the basis of Geddes method, the distribution characteristic of friction surrounding pile of composite foundation is showed as small in top and bottom and big in middle according to measured results, the calculation formula of the top surface of stratum additional stress has been deduced by using Mindlin and Boussinesq solution, settlement calculation method is brought forth simultaneously.(3) Optimization design principle of long-short-pile composite foundation is put forward, base on which replacement ratio and pile length is taken as design variable, bearing capacity, settlement, stratum strength and other demands acted as constraint function, pile cost taken as objective function, so the optimization design model of long-short-pile composite foundation is built.(4) Intelligent optimization design method of long-short-pile composite foundation are introduced based on genetic algorithms and simulated annealing, and corresponding optimization design calculation program is worked out. Practical results show that the presented method is feasible, and it will get the purpose that optimization design and cost saving, it has extensive application prospect.(5) The stress and displacement field characteristic of long-short-pile composite foundation is analyzed by large finite element software Marc, the variety rule of...