炭质板岩横观各向同性强度准则及参数辨识方法

Transverse Isotropic Strength Criterion and Parameter Identification Method for Carbonaceous Slate

为探究层理状岩石的横观各向同性力学特性,以炭质板岩为研究对象,通过室内试验和理论分析对其强度准则和参数辨识方法进行研究。首先,对水平与垂直层理岩样开展不同围压的常规单、三轴压缩试验,探讨不同应力状态炭质板岩的强度特性与破坏模式。其次,对比分析试验结果,建立适用于炭质板岩的横观各向同性弹塑性本构模型;基于Pariseau强度准则确定模型的屈服函数,用以描述炭质板岩不同方向的强度特性;基于相关联流动法则确定模型的塑性势函数,用以描述炭质板岩塑性变形阶段的流动方向。在各向同性假定下,该模型可退化为描述各向同性岩土材料的Drucker-Prager模型。最后,提出模型参数辨识方法,即通过常规三轴压缩试验和经验公式求解弹性参数;通过基于Duveau数值计算程序的最小二乘法常规三轴试验和直线型Mohr-Coulomb准则确定岩样的抗压、抗拉和剪切强度,再代入所推导公式求解塑性参数;结合试验结果验证了所提横观各向同性强度准则的合理性。结果表明:不同围压的水平岩样的抗压强度均高于垂直岩样,且抗压强度随着围压的增大基本呈线性增大;炭质板岩在压缩过程中多呈脆性破坏,水平层理岩样呈滑移-剪切破坏,垂直层理岩样呈张拉-剪切破坏。

To study the transverse isotropic mechanical properties of layered rock,the strength criterion and parameter identification method for carboniferous slate were studied by using laboratory test and theoretical analysis.First,the conventional uniaxial and triaxial compression tests with different confining pressures were carried out on horizontal and vertical stratified rock samples to investigate the strength characteristics and failure modes of carboniferous slates under different stress states.Second,the transversely isotropic elastoplastic constitutive model for carbonaceous slate was established by comparing and analyzing the experimental results.The yield function of model was determined based on the Pariseau strength criterion to describe the strength characteristics of carboniferous slate in different directions.The plastic potential function of model was determined based on the associated flow rule to describe the flow direction in the plastic deformation stage of carbonaceous slate.Under the assumption of isotropy,the model can be degraded to Drucker-Prager model for describing isotropic geotechnical materials.Finally,the identification method of model parameters was proposed,in which the elastic parameters were solved by conventional triaxial compression test and empirical formula;the compressive,tensile and shear strengths of rock samples were determined with the least square method based on Duveau numerical calculation program,conventional triaxial tests,and linear Mohr-Coulomb criterion.Then the plastic parameters were solved by substituting them into the derived formulas.The rationality of proposed transverse isotropic strength criterion was verified by combining the experimental results.The result indicates that the compressive strengths of horizontal rock samples under different confining pressures were higher than those of vertical rock samples;the compressive strength increases linearly with the increase of confining pressure.The carbonaceous slate is usually brittle failure during compression,the horizontal bedding rock is slip-shear,and the vertical bedding rock is tensile-shear.