Circular Shallow Foundation Bearing Capacity Limit Analysis And Numerical Simulation,

Shadow foundation bearing capacity is one of the most important research topics in the field of geotechnical engineering. Since the formation of soil mechanics, substantive investigation and feasibility study have been conducted both at home and abroad, and a series of achievements have been made. Because of its great practical value in engineering application, this dissertation, based on the achievements summed up by our predecessors, tries to make a thorough, in-depth and systematic research on the subject.At the present time, there are mainly three theoretical methods to determine the ultimate bearing capacity of soil foundation:limit equilibrium method, slip line method and limit analysis. As the limit equilibrium method is not accord with soil damage characteristics under the limit state, and the solution is uncertainty, therefore, its safety was questioned; Adopting the slip-line method can get complete solution only about the weightless soil and some boundary conditions which is relatively simple, and its amplification is restricted to a certain degree; Based on the energy principle, limit analysis method bypasses the plastic deformation phase of soil damage, researches external power and internal energy dissipation rate to solve the ultimate load bearing capacity when the soil occurs unrestricted plastic flow, which greatly simplifies the solution process and being widely used.Focusing on circular shallow foundation, this thesis chooses a suitable foundation failure mode and motor displacement velocity field, considers the influence of the lateral soil pressure on the limit bearing capacity of circular shallow foundation for the first time and the effects of soil weight under the base of the foundation and surcharge load according to the theory of limit analysis from the perspective of spatial problem, presented a more reasonable upper-bound solution for the ultimate bearing capacity of the three-dimensional circular shallow foundation in theorem and the corresponding bearing capacity factors Nc, Nq, Nr.The bearing capacity factors are compared with the modified Prandtl-Vesic and K.Terzaghi bearing capacity factors and proved to be more reasonable. At the same time, selecting an appropriate soil constitutive model and using FLAC-3D to simulate the circular shadow foundation, the numerical results are compared with the upper bound solution, and the upper-bound solution in this paper proved to be more rational and practical.