基于应力和时间双重影响下岩石蠕变模型研究

Research on rock creep model based on dual effects of stress and time

为了更好地描述岩石蠕变的全过程和表征加速蠕变阶段的变形特性,研究岩石蠕变力学机理并引入弹塑性损伤体,改进广义开尔文蠕变模型,进而构建1个可反映岩石加速蠕变变形特征的弹塑性损伤体蠕变模型,并提出一种确定蠕变模型参数的方法;通过室内三轴蠕变试验计算出不同时间和应力作用下的蠕变参数,分析不同应力作用下蠕变参数与时间关系,揭示蠕变参数劣化的实质和岩石蠕变变形破坏的机理。研究结果表明:当岩石的体积压缩状态转化为扩容状态后,体积模量的绝对值随蠕变应力增大而减小,且随应力水平增大以及时间推移,岩石的蠕变扩容效果越来越明显;而损伤影响程度系数反映了在蠕变变形过程中岩石内部损伤程度,当损伤影响程度系数增大时,岩石内部的损伤程度以及岩石的加速蠕变变形也越大;通过分析蠕变参数在时间作用下劣化规律,验证了该方法是合适可行的,且建立考虑应力和时间双重影响的蠕变模型,也较好地模拟了岩石从衰减蠕变到加速蠕变的变形全过程,同时更加准确地反映了岩石的衰减和稳定蠕变阶段的蠕变特性。

Determining the parameters of creep model and constructing a constitutive model that can describe the accelerated creep stage of rocks are difficult issues in analyzing creep characteristics.To effectively describe the entire process of rock creep and characterize the deformation characteristics at the accelerated creep stage,the generalized Kelvin creep model was improved by studying the rock creep mechanics and introducing elastoplastic damage bodies.Furthermore,a creep model of elastoplastic damage body that can reflect the characteristics of accelerated creep deformation of the rock was constructed.A method to determine the parameters of the creep model was proposed.The creep parameters at different time and stresses were calculated through laboratory triaxial creep test.By analyzing the relationship between creep parameters and time under different stresses,the essence of creep parameter degradation and the mechanism of rock creep deformation failure were revealed.The results show that the absolute value of the volume modulus decreases with the increase of the creep stress when the compression state of the rock changes to the dilatancy state.The creep dilatancy effect becomes increasingly obvious with the increase of stress level and the passage of time.The degree of damage influence coefficient controls the degree of damage inside the rock during creep deformation.When the degree of damage influence coefficient increases,the degree of damage inside the rock and the accelerated creep deformation of the rock also increase.By analyzing the degradation law of creep parameters under the action of time,the method to determine the creep parameters is suitable and feasible.Considering the influence of stress and time on creep parameter degradation,the new creep model that can effectively simulate the entire process of rock deformation from attenuation creep to acceleration creep is established.The model can also accurately reflect the creep characteristics of the decay and stable creep stage of the rock.