Experimental study and modeling of shear rheology in sandstone with non-persistent joints

Understanding the long-term mechanical behavior of cracks in rock masses is important for engineering projects and for controlling rock mass stability, particularly on rock slopes. In this study, laboratory-prepared cubic sandstone samples with non-persistent joints were subjected to shear creep testing using a rock shear rheometer. The results indicate that long-term shear strength is influenced by the long-term internal friction angle and cohesion, and decreasing cohesion is a key factor for changes in long-term shear strength under constant load. Additionally, damage to the shear modulus is related to the initial damage conditions and joint persistence of the samples. A new creep model is developed that considers the effect of crack or joint length on time-dependent rock behavior. The elasto-viscoplastic behavior of non-linear creep is also described. The modified shear creep model shows promising results for estimation of failure time, shear creep deformation and long-term stability of a rock slope for cases where planar-type failure occurs along a crack or joint surfaces in which no cohesion exists in the crack or joint surface contacts.