Solution and error evaluation for bearing capacity of rough strip footings

The slip-line method is used to calculate the bearing capacity of rough strip footing on ponderable soil. This method takes account of the influence of cohesion c, friction angle φ and unit weight γ of soil in one failure mechanism, and thus avoids assuming the shape of slip surfaces. Moreover, the solution of this method strictly satisfies all the given boundary conditions. The accuracy of the solution is proved by comparing with the published results. The investigations on the influence factors of N_γ show that the bearing capacity factor N_γ of the rough strip footing is related to the surcharge ratio λ besides the friction angle φ. A curve-fitting-based formula is proposed to get the exact N_γ on the basis of the curves between N_γ and λ under different φ. The results from the suggested formula have the maximum errors within ±4%. Finally, the errors between the bearing capacity obtained by the superposition method and the exact solutions are evaluated. The relationship of the error ε and λ under different φ reveals that the superposition results are less than the exact ones with the largest error occurring when λ varies between 0.1 and 1.