Evaluation of the method of stress characteristics for estimation of the soil bearing capacity

Abstract EN

The classical bearing capacity theories rely on the superposition of three separate bearing capacities–a technique that is inherently conservative – but they also rely on tabulated or curve-fitted values of the bearing capacity factor, Ny, which may be conservative.

Further approximations are introduced if the footing is circular (multiplicative shape factors are used to modify the plane strain values of, Nc, Nq and Ny) or if the soil is non-homogeneous (calculations must then be based on some representative strength).

By contrast, the method of stress characteristics constructs a numerical solution from first principles, without resorting to superposition, shape factors or any other form of approximation.

In this paper, the validation of the method of stress characteristics is tested by solving a wide range of bearing capacity problems.

The results are compared with classical bearing capacity theories; namely, Terzaghi, Myerhof, Hansen and Vesic methods.

It was concluded that the bearing capacity predicted by the method of stress characteristics for the case of a circular footing in clay ranges between (3.7 – 4.0) greater than Terzaghi, Meyerhof, and Vesic methods.

This means that the method is not conservative for this case and can be dependent for economic design of foundations.

The bearing capacity predicted by this method increases linearly with (D / B).

For all values of the angle of friction, ∅, the method reveals bearing capacity values for smooth footings greater than Terzaghi and Hansen and smaller than Meyerhof and Vesic theories.

Considering the foundation to be rough, the method gives bearing capacity values greater than all other methods.

The difference increases as the angle of internal friction (∅) increases.

This makes the method unreliable for rough foundations.