初始裂纹对泥岩单轴压缩力学性质影响的FDEM研究

Investigating the effect of initial cracks on the mudstone mechanical behavior under uniaxial compression using FDEM

要为研究初始裂纹对泥岩试件单轴压缩力学性质的影响, 首先, 对经过不同温度处理后的泥岩试件开展单轴压缩力学实验. 然后, 运用有限元-离散元耦合方法(FDEM)建立含有不同数量初始椭圆裂纹的单轴压缩数值模型来模拟室内实验. 最后, 建立一个分段损伤 模型揭示单轴压缩损伤演化过程. 通过研究发现模拟的应力-应变曲线与实验结果存在较好一致性, 实验和数值结果表明初始裂纹密度 对单轴压缩力学特性存在重要影响, 尤其是随着初始裂纹密度的增加, 初始非线性特征越明显, 而弹性模量和单轴抗压强度有所下降. 同时初始裂纹密度越大, 扩展的裂纹数量越少, 张拉破坏模式则越明显. 此外, 分段损伤本构模型能够很好地对应模拟和实验中的应力- 应变曲线. 对于初始非线性比较明显的岩石材料, 应该将岩石的损伤演化过程划分为初始损伤、损伤减少和损伤增加三个阶段.

For investigating the effect of the initial cracks on the mechanical characteristics of mudstone specimens under uniaxial compression,firstly,uniaxial compression tests on mudstone specimens treated by different temperatures(20°C,30°C,60°C and 80°C,respectively)were carried out.Then,some uniaxial compression numerical models containing the certain number of initial elliptical cracks were built using finite-discrete element method(FDEM)to simulate laboratory tests.Lastly,a piecewise damage model was established to reveal the damage evolution process.It is found that the modelling results present a well agreement with laboratory tests in the aspect of stress-strain response.The test and simulation results reveal that initial crack density has a significant influence on the uniaxial compression mechanical characteristics.Specifically,with the increasing initial crack density,the initial nonlinearity is more obvious,but the elastic modulus and uniaxial compression strength are in decrease.And the cracking event counts are in decrease as increasing the initial crack density while the open fracturing mode is more dominant.Furthermore,the piecewise damage model can reproduce the stress-strain curves finely.If the initial nonlinearity is obvious,it is feasible to divide the damage evolution process into initial damage,damage decrease,and damage increase stages.