A grain-based time-to-failure creep model for brittle rocks

Abstract

Long-term stability analysis and stand-up time prediction of underground excavations are important in engineering design and construction. A Time-to-Failure (TtoF) creep model is proposed for the simulation of lifetime of intact brittle rock under uniaxial and triaxial loading conditions. In the TtoF model, the grain-based modeling approach using UDEC is adopted to describe the heterogeneity and micro-fractures of rock. The time-dependent deformation behavior of a grain cell is assumed to obey the Burgers creep model. The viscosity coefficient of the Maxwell component is modified to relate it to stress. The time to enter the acceleration creep deformation stage is considered as a function of the stresses and the strength parameters of the grain cell. A damage index is defined as a function of the strength parameters and the center-driving-stress ratio at a given time. Degradation of grain boundary is considered to measure the roughness corrosion of contact. The validity of the TtoF model is verified using laboratory uniaxial and triaxial compression test data of brittle rocks. The model can be useful for investigating time-dependent deformation behaviors of brittle rock and determining stand-up time of rock structures.