基于扰动因子的软岩扰动蠕变本构模型
Constitutive model of soft rock disturbance creep based on disturbance factor
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摘要: 动力扰动下处于极限强度的深井软岩巷道围岩具有流变变形量大,变形速率快的变形特征,致使软岩巷道支护困难和灾害频发。为了研究软岩在动力扰动下蠕变破坏特征及本构模型,通过自主研制的岩石扰动蠕变实验系统对泥页岩进行了分级加载流变实验,试验结果表明:非稳定蠕变曲线在扰动前后流变变形明显不同,当施加应力水平较小时(处于第Ⅰ,Ⅱ蠕变阶段),每次扰动的瞬间会使岩石应变突变,但突变值随后逐渐回弹,最终岩石变形速率趋于一个稳定值;当应力水平较大时(处于第Ⅰ,Ⅱ蠕变阶段),岩石经过多次扰动后,当积累能量达到岩石破坏能量时,诱使岩石发生加速流变,而原处于蠕变第Ⅲ阶段的岩石的蠕变速率加快,缩短了岩石破坏的时间。基于岩石扰动状态理论,提出一个以扰动能量和扰动次数为自变量的扰动因子函数,以它为权重函数与NRC模型有机结合,建立了软岩流变扰动效应的本构模型并对模型参数进行识别,结果表明理论曲线与实验曲线吻合较好,验证了该模型能够正确性地描述动力扰动下软岩蠕变特征,该成果对于深部地下工程的稳定性研究具有参考价值。Abstract: The surrounding rock around soft rock roadway in deep mine with dynamic disturbance has the characteris-tics of large rheological deformation and rapid deformation rate,which may lead to difficulty in supporting and frequent disasters. In order to study the characteristics and constitutive model of the soft rock creep damage with dynamic dis-turbance,using self-developed rock disturbance creep experimental system,a multi-stage loading creep experiment of the mud shale is carried out under dynamic disturbance. The experimental results show that the rheological deformation of the rock unsteady rheological curve is significantly different before and after the disturbance. When the stress level is relatively small,its strains happen to change suddenly after disturbance at the first and the second creep stage,then gradually take a very small rebound,eventually the rock deformation tends to a stable value. When the stress level is relatively high,the repetitious disturbance to the rock at the first and the second creep stage leads to the acceleration stage of rheological rate when the accumulation of energy in rocks reaches to the destroy energy. At the third creep stage under dynamic disturbance,the rock creep rate is accelerated and the time of rock failure is shortened. Based on the disturbance theory,the disturbance power and disturbance frequency as independent variables,a disturbance factor function is derived. Combining with the NRC model,a disturbance rheological constitutive model is proposed and the model parameters are identified. The results show that the theoretical curves are in good agreement with the experimen-tal curve,which verifies the model is able to describe the soft rock creep characteristics with dynamic disturbance. The result has a reference value for the study of stability of deep underground engineering project.