The application of a Matsuoka-Nakai-Lade-Duncan failure criterion to two porous sandstones

We summarize two suites of recent true triaxial tests in two porous sandstones, Coconino and Bentheim. One suite of tests conducted under constant sigma(2) and sigma(3), which revealed the effect of sigma(2) and sigma(3) on rock failure. The other suite of tests, performed under constant Lode angle, determined the failure dependencies on mean stress and Lode angle. Building and modifying failure descriptions by Matsuoka-Nakai (MN) and Lade-Duncan (LD), an explicit failure criterion (modified-MNLD) that generalizes a class of failure forms is used to fit the novel loading path data of both sandstones. The determined failure descriptions fit both rocks well over a wide range of failure conditions. Then, the generated failure descriptions were further used to predict failure conditions under the constant sigma(2) and sigma(3) loading path. The predictions by the modified-MNLD are generally consistent with these data. The predictions also successfully replicated the variation of sigma(1,peak) with sigma(2) under constant sigma(3), suggesting the potential of the modified-MNLD to clarify the effect of sigma(2) on rock failure.