Stress-induced anisotropy and loading path effects on borehole responses

Abstract

In conclusion, the conceptual results presented in this note show that attempting to model stress development around an underground excavation using only a simple constitutive model can give misleading results. Two constitutive models, written within the same mathematical framework of an incremental linear model under a monotonic loading and giving exactly the same rock response during triaxial tests, can lead to predicting widely different behaviour. It must therefore be concluded that despite their simplicity and flexibility, the use of such models must be handled with caution especially when complex stress paths are considered which differ significantly from the simple triaxial test load path. It is recommended that the validity of a constitutive model should be checked by analyzing and comparing the results of carefully monitored hollow cylinder tests performed either by increasing the outer pressure or decreasing the inner pressure. Nevertheless, it should be kept in mind that for engineering applications a model should remain simple and reliable.