Study On Bearing Capacity Of Foundations With Different Roughness

The method of characteristics (also known as the slip line method) is a traditional method to solve the classical geotechnical bearing capacity problem of a rigid foundation, resting on a cohesive-frictional soil mass, loaded to failure by a central vertical force. This paper describes the use of the method of characteristics to establish plastic collapse loads of footings with arbitrary roughness.On the assumption that the soil is at yield, the two-dimensional stress state at a point can be fully specified in terms of two auxiliary variables, namely the mean stress σ and the orientation θ of the major principal stress, together with the radius of Mohr's circle R. The governing equation can be then obtained after associating Coulomb yield criterion with the equilibrium equation.Considerable importance should be attached to the treatment of boundary conditions of soil-footing interface. In this paper, boundary conditions of footings with faculative roughness are analyzed in detail, which makes it possible to apply the finite difference scheme to solve the governing equation with any combination of the parameters c,φ,γ,B and q.When constructing stress field under rough footings, it is convenient to adopt a new technique which makes the most of the symmetry condition. A computer progam is then developed to testify the validity of the technique and solve several example problems.In practical engineering, bearing capacity factors N_c, N_q, N_γ are widely used to calculate ultimate bearing capacity of foundations. Therefore, a simple and effective method is adopted to obtain values of N_c, N_q, N_γ regarding footings with different roughness.Finally, the problems requiring further studies are discussed.