Research On The Raft Foundation Internal Force And Groundsill Deformation With Coordination Deformation

With the development of high-rise buildings, researches on their foundations have become a focus of construction engineers. Finding favor in engineers'eyes, raft foundation has been widely used in construction of tall buildings because of its advantages such as full effectiveness of ground bearing capacity, small foundation settling amount, strong adjustment ability of uneven foundation settlement and convenience for application during real construction. However, too many factors have to be taken into account when the simulation of raft foundation is carried out. Moreover, stress mechanism of raft foundation is still a twilight zone. Tradition calculation method, making mutual influence between foundation and groundsill and that of different soil bodies beyond consideration, caused a large difference of simulation results from actual measurement and finally the direct function of simulation is quite discounted. Based on the urgency of engineering requirement, a calculation method of foundation stress was tried to be proposed with reasonableness, concision and practability.Firstly, the compressed layer model of foundation based on the layer wise summation was adopted. The net foundation pressure was analyzed by corner-points method and Boussinesq method and the resulted calculation equation was deduced to a form easily used when conducting calculation. Both the base plate and the interface between the groundsill and foundation were dispersed to several rectangular elements. All elements were connected by their joints. The ground flexibility coefficient was obtained before a conversion to gaining the foundation stiffness coefficient. Consequently, a newly constructed calculation model of foundation stiffness was completed. Then, the calculation model was combined with finite element method to execute finite element analysis of a numerical example on the basis of deflection continuity and force balance at joints. Finally, the above method was applied to complicated soil of a case example to study its accuracy on simulating groundsill deformation under the action of flatbed raft foundation.The study results showed that a smaller settling amount of the numerical example was acquired by finite element analysis than criterion method. Results of the case example from simulation, engineering survey and calculation under criterion method, were compared and exhibited more accuracy of simulation than conventional method. The settlement and deformation of groundsill and foundation was considered satisfying static equilibrium and deformation compatibility in the proposed method. The guiding significance to theoretical researches and engineering application would be expected for its definite physical meaning, simple and convenient calculation process and trusty results.