基于塑性扩张的岩石变参数蠕变损伤模型与工程应用

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

为研究岩石蠕变损伤过程与围岩塑性区扩展之间的内在联系,建立基于塑性扩张的变参数蠕变损伤模型（BNMC模型）,该模型认为岩石塑性屈服面随蠕变时间动态变化,在σ-τ空间内,强度包络线随蠕变时间的增加而逐渐内移。采用线性插值法对该模型各蠕变参数进行处理,获得任意连续偏应力水平对应的蠕变模型参数,从而实现BNMC模型的数值化。采用该模型对金川二矿区-1 098 m水平中段下盘运输巷的蠕变变形进行数值模拟,对比研究未支护裸巷和喷锚支护巷道的蠕变变形规律。研究发现,未支护裸巷围岩塑性区边界不是一成不变的,而是随时间的发展,塑性区边界逐渐向外扩张,围岩承载力逐渐下降,从而导致围岩加速蠕变显现,巷道蠕变失稳;通过对喷锚支护巷道的蠕变数值模拟结果和多点位移计实测结果的对比,发现数值模拟曲线与实测曲线在走势上基本吻合,但在量值上实测蠕变位移值要略大于数值模拟结果;由于支护与围岩的相互作用,支护在一定程度上改变了围岩的偏应力状态和位移,阻止了围岩塑性区边界扩张,喷锚支护巷道在0-200 d的蠕变计算时段内,未呈现出加速蠕变性态。

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 roadway 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.