Durability prediction of brittle rocks based on type-I crack extension theory

Abstract

When subjected to long-term static loading, with the accumulation of damage and fracture, brittle rock would fails when the static loading is lower than the compressive strength of the rock, and the increasing of the static loading can generally shorten the time required for the brittle rock failure. To explore the relationship between the durability of the brittle rock and the applied static loading, in this paper, the propagation modes of the microcracks in brittle rock under the static loading in the subcritical crack growth stage are uniformly attributed to the tensile mode, and the total time required for microcrack propagation in the subcritical crack growth stage is chosen as the criterion for judging the durability index of brittle rock. Based on the Maxwell model, the local effective tensile stress that drives crack propagation is derived. The phenomenon of brittle rock exhibiting tensile failure under the compressive stress is preliminarily explained, and the corresponding requirements for this phenomenon to occur are also presented. A new expression of rock durability prediction with a clear physical meaning is established. The key parameter, i.e., the durability index “n” in the newly derived expression is obtained through fitting, and the relationship between the durability index and the rock type is preliminarily analysed. This study may provide an approach for preliminarily estimating the durability of brittle rock.