Effective Stress Coefficient of Rocks for Peak and Residual Strengths

The determination of effective stress is an important aspect of stability analysis, and has a number of engineering applications especially in geotechnical and petroleum engineering, including underground and surface rock structures, oil and gas production, and sequestration of carbon dioxide [Alam et al., 2009; Alam et al., 2010; Hu et al., 2010]. Failure criteria for porous media are represented using the effective stress, the concept of which was first introduced by Terzaghi (1936) for soil, and is commonly known as Terzaghi's effective stress principle. It states that the effect of the total stress σ and the pore pressure P p can be described using a single parameter, which is known as the effective stress σ ʹ , and is defined as follows: