Calculation of improved bearing capacity factors and earth pressure coefcients using plasticity methods

In the zone of soil below a foundation, the major principal stress ′σ1 (or σ1 in a total stress analysis) is vertical. In the zones of soil to each side, the major principal stress is horizontal. There is therefore a 90° rotation in the direction of the principal stresses between the active zone beneath the footing and the passive zones on each side. In the stress eld analyses of shallow foundations presented in Section 8.2, this 90° rotation in the major principal stress direction was achieved in one ‘jump’, across a single frictionless stress discontinuity (Figure 10.1a).