Rock creep damage model with varying parameters based on plastic expansion and engineering application

To study the relationship between the creep damage and plastic zone expansion of surrounding rock,a creep damage model with varying parameters(BNMC model),based on the plastic expansion laws,was established in which the plastic yield surface of rock changes dynamically and the strength envelope moves inward gradually with creep time in the space of σ-τ. A linear interpolation method was proposed to obtain creep parameters at arbitrarily continuous deviatoric stress level,so as to realize the numerical simulation of BNMC model. The numerical simulations for the transport roadway creep deformation in the foot wall at the middle of -1 098 m level in Jinchuan No. 2 Mining District were performed. The creep deformation characteristics in the nude roadway and the roadway with combined bolting and shotcrete were comparatively studied,respectively. The results are as follows:the plastic zone boundary of nude road-way is gradually expanded outwards with time,rather than static,which leads to a gradual decrease in the bearing ca- pacity of surrounding rock,the appearance of accelerated creep and roadway creep instability. Based on the comparison between the numerical simulation results and the measured results by multi-point displacement meters for the roadway with combined bolting and shotcrete,the creep deformation curves of numerical simulation show a consistent trend with the measured curves,although the latter is slightly larger than the former in magnitude. Due to the interaction between the supports and surrounding rock,the supports change the deviatoric stress state and displacement of the surrounding rock to some extent,and prevent the plastic zone from expanding,the roadway with combined bolting and shotcrete fails to show acceleration creep in the creep duration of 200 d.