一种横观各向同性岩体蠕变模型

A creep constitutive model for transversely isotropic rocks

层状岩体由于层理面或者结构面的存在,在力学上具有横观各向同性的特点,现有的各向同性蠕变模型难以全面反映横观各向同性岩体的蠕变力学特性。为构建能够反映横观各向同性岩体的三维蠕变模型,以能反映瞬时应变、减速蠕变和稳态蠕变特征的黏弹性Burgers模型为基础,基于常泊松比假定,在三维各向同性蠕变本构方程的基础上,按照算子替换的方法,将横观各向同性柔度矩阵代替各向同性柔度矩阵,并考虑了平行和垂直层理方向岩体蠕变力学行为的差异性,推导了横观各向同性岩体的三维蠕变本构方程。根据本构方程的特点,提出了根据平行和垂直方向岩体蠕变试验结果进行三维蠕变本构模型中蠕变参数的辨识方法。将提出的模型应用于三轴蠕变试验参数辨识,从而获得了一套完整的三维蠕变参数,并与试验结果进行对比分析,从而验证了所提模型与方法的合理性和有效性。进一步,指出了传统蠕变试验设计方案的局限性,给出了横观各向同性材料蠕变试验设计建议。研究成果为研究岩体三维蠕变机制提供了新思路,可对岩体蠕变试验设计提供相应的科研支撑。

Due to the presence of bedded or jointed planes,layered rock mass shows transversely isotropic characteristics in mechanics.Therefore,the existing isotropic creep model is difficult to fully reflect the creep constitutive model of transversely isotropic rock mass.In order to obtain the three-dimensional transversely isotropic creep constitutive model,the Burgers model is adopted to describe the characteristics of instantaneous strain,decaying creep and steady creep of transversely isotropic rock mass.Based on the assumption of constant Poisson’s ratio and three-dimensional isotropic creep constitutive equation,a three-dimensional creep constitutive equation of transversely isotropic rock mass is derived through differential operator method by substitution of transversely isotropic compliance matrix into isotropic compliance matrix.The new model also takes the differences of creep behaviours between specimens with horizontally and vertically oriented bedding into account.According to the characteristics of creep constitutive equation,a method for identifying the creep parameters in the three-dimensional creep constitutive model is proposed based on the creep test results.The model is applied to the identification of triaxial creep test parameters,and a comprehensive set of three-dimensional creep parameters are obtained.The rationality of the proposed creep equation is verified by comparing theoretical values with experiment results.The limitations of the traditional creep tests design scheme are further pointed out and some suggestions for creep tests design of transversely isotropic materials are given.The research results provide a new insight for the study of three-dimensional creep mechanism of rock mass and provide scientific support for the design of rock mass creep tests.