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AbstractThe field bearing plate method test is the most commonly used method to determine rock mass deformation parameters. Currently, due to the effect of the applied test stress, the difference between the rheological model curve and test curve can be significant, namely the model cannot reflect the effect of the applied stress. In this study, a seven-component viscoelastic combination model that considers the effects of stress is proposed. Based on the proposed viscoelastic combination model and viscoelastic theory, the viscoelastic analytical solutions for the bearing plate tests are derived. Then, the viscoelastic characteristics of rock mass aging deformation as well as the effect of viscoelastic parameters on rock mass aging deformation are discussed. After that, a flexible bearing plate test and a rigid bearing plate test are carried out respectively, based on which the optimal rheological models and corresponding parameters of the rock mass aging deformation are identified according to the optimisation inversion method. Results indicate that the proposed combination rheological model with two Kelvin bodies is more preferable then that with only one Kelvin body. The bearing plate tests and the model parameters identification manifest that the proposed viscoelastic combination model is effective and reasonable.

AbstractUnder the long-term effect of high stress, the stability problem caused by the time-dependent deformation of brittle surrounding rock in deep engineering is becoming more and more prominent. The accurate description of the effectiveness of brittle rock is an important basis for the prediction of mechanical response and the stability evaluation of surrounding rock in deep engineering. To describe the accelerated time-dependent deformation behavior of brittle rock, a Newtonian body with non-constant parameters considering the effects of stress state is proposed. Combined with the improved Burgers model, a viscoelastic model with non-constant parameters of brittle rock is developed. The effects of time, delay coefficient, and stress level on the viscosity coefficient, as well as the influence of delay coefficient and initial viscosity coefficient on the accelerated time-dependent deformation, are examined. The results show that (1) the viscosity coefficient decreases with time and increases with the delay coefficient, while the attenuation rate increases; (2) the viscosity coefficient decreases with increasing stress level, and its attenuation rate increases with time; (3) with the increase of the delay coefficient, the nonlinear characteristics of the accelerated phase of the rock time-dependent deformation curve become more and more obvious; and (4) as the initial viscosity coefficient increases, the nonlinear characteristics of the accelerated phase of the time-dependent deformation curve become less and less obvious. The above laws fully reflect the evolutionary law of the nonlinear time-dependent deformation of rock. By comparing the results of the marble creep test with theoretical predictions, we found that when the stress limit is exceeded, the established model can well describe the initial attenuation, steady state, and accelerated characteristics of the rock time-dependent deformation curve, thus verifying the ability of the proposed model to describe the accelerated creep behavior, as well as the overall rationality of the model.