Effects of Confining Pressure on Intact Rocks’ Anisotropy: Fid-Bau Portal

Effects of Confining Pressure on Intact Rocks’ Anisotropy

Chawre, Bharti / Gupta, Sachin

A “pattern” in the rock material, such as schistosity, foliation, or bedding, frequently causes anisotropy, which makes the qualities of the rock’s material directional dependent. Generally, rocks’ mechanical characteristics are described in the terms of strength. Therefore, in this study, only this parameter is taken to reflect the anisotropy. The strength anisotropy of intact rocks is prominently affected by the orientation angle and the magnitude of the confining pressure. So, in this study, three types of metamorphic rocks (schists, genies, and quartzite) from project sites in the Himalayan region have been examined by two different methods to ascertain the effect of the confining pressure (σ₃) on strength anisotropy. These methods are based on calculating the intensity of the strength anisotropy. (K₁) and the coefficient of strength anisotropy (f). The results of this study show that the confining pressure has a significant impact on strength anisotropy. As the confining pressure increases, the laminated structure of the rock samples consolidates and starts to behave like an isotropic material, which reduces the anisotropy effect. It has also been noted that schist and gneiss’s behaviour is almost identical to both of the proposed methods, except for quartzite. This study suggests that even for rocks with the same lithology, not all types of rocks can be predicted accurately by the general equation. To find other parameters, additional research is necessary. Although anisotropy can be crucial to the stability of underground excavations and subsequent geotechnical design, anisotropic properties of the rock are typically not taken into account in geotechnical designs. However, analytical techniques should take strength anisotropy into account in order to predict failure processes.