Anisotropic Deformation Model for Hawkesbury Sandstone Incorporating Inherent Mobilised Shear Strength

An extensive study on modelling progressive Hawkesbury Sandstone degradation by anisotropic deformation subjected to monotonic loadings is presented and discussed in this study. Hawkesbury Sandstone was used due to its unique behaviour, which was initially assumed to be a uniform testing lithology with respect to grain size, compressive strength and stiffness. This study identified a theoretical approach to the anisotropic model of rock deformation. The model utilizes the stress-strain curve to derive the development of mobilised shear strength and applies it to the rock to simulate how it compresses in anisotropic. Monotonic loading tests were performed in triaxial conditions at variations of confining pressure, 4MPa and 8MPa. An increment of confining pressure was used to obtain elevation in the stress-strain curve. Progressive monotonic loading changed the mechanical characteristics of the rock; the level of the applied stress is compressed axially and then expanded laterally. During applied loading, the rock may experience damage or rock failure; the correlation between the magnitude of the mobilised shear strength and the axial stress associated with it is regarded as an intrinsic property in the rock mass. The stress-strain behaviour of rocks under anisotropic stress conditions can be predicted using this method. The mobilised minimum friction angle is used to determine the location of the mobilised shear strength envelope. The results reveal that the mobilised intrinsic shear strength is developed if the rock is forced to compaction. This is evidenced by the envelope rotating upward to the shear force envelopes during failing. Consequently, it can be deduced that the cementation (c') of the rock increases.