考虑强度参数劣化的砂岩非定常蠕变模型研究

Research on unsteady creep model of sandstone considering strength parameter deterioration

为了更好地研究岩石在不同应力作用下的蠕变变形特性,采用TAW-2000岩石试验系统对围岩开展了单轴蠕变试验;将西原体模型蠕变参数转化为关于时间的函数,且将强度参数也转化为关于时间的函数,进一步将屈服函数非线性化,构建出一种新型的非定常分数阶蠕变模型,并通过试验数据来验证模型的正确性与合理性。结果表明:轴向蠕变变形总体上随应力水平的增加而增加,但蠕变变形占总变形的比例先增大再减小,反映了试样内部结构的不断损伤与劣化过程;该模型不仅准确地反映了衰减和稳定蠕变阶段的蠕变特性,也克服了传统西原体模型难以描述加速蠕变的缺点;同时考虑到蠕变参数随应力和时间变化发生的劣化,可以更好地描述不同应力状态下岩石的蠕变损伤过程,为建立非定常蠕变模型和确定模型参数提供一个新的思路。

In order to better study the creep deformation characteristics of rocks under different stresses,uniaxial creep tests were performed on surrounding rocks using the TAW-2000 rock test system.The Nishihara model creep parameters are transformed into a function of time.The strength parameter is also converted into a function with respect to time,and the yield function is further nonlinearized.Then,a new type of unsteady creep model is constructed,and the correctness and rationality of the model is verified by experimental data.The results show that axial creep deformation generally increases with increasing stress level,but the proportion of creep deformation to total deformation increases first and then decreases.This also indirectly illustrates the damage effects of stress on the rock.This model not only accurately reflects the creep characteristics of the decay and stable creep stages,but also overcomes the shortcomings of traditional Nishihara model,which is difficult to describe accelerated creep.At the same time,considering the deterioration of the creep parameters with stress and time,the creep damage process of rocks under different stress states can be better described.This provides a new idea for establishing unsteady creep model and determining model parameters.