Analysis of boundary value problems in soil plasticity assuming non-coaxiality

In solutions of boundary value problems in soil engineering, it is usually assumed that the stress and velocity fields are coaxial. Some researchers have argued the validity of this assumption. This paper investigates the influence of this simplifying assumption on the solution in these problems. The zero extension line method has been used for this investigation. The theory of the method has first been extended to the more general case of non-coaxial fields of velocity and stress in soils. A computer code has been written which can solve the given boundary value problem assuming coaxiality or non-coaxiality. The rotation of rough and smooth strip footings into loose and dense sands has been provided as an example of a typical boundary value problem. The analyses have been performed once with and the other without assuming coaxiality. A comparison of the results indicates that higher loads are required for the same deflection when coaxiality is assumed. It is therefore recommended to consider the non-coaxiality in the analysis if the soil really behaves so; otherwise the obtained result would not be correct