气孔杏仁状玄武岩随机三维模型构建与单轴压缩力学行为研究

Stochastic three-dimensional modeling and the mechanical behavior of vesicular amygdaloidal basalts under uniaxial compression

为了研究初始孔隙对气孔杏仁状玄武岩力学行为的影响规律,提出了一种考虑计算孔隙率、体积参数、形状参数、角度参数和构造参数的气孔杏仁状玄武岩随机三维模型构建方法,基于建立的随机模型开展了五因素五水平的单轴压缩正交数值模拟,分析不同模型的应力-应变曲线、破坏模式和破坏特征。结果表明:计算孔隙率、角度参数和构造参数对于岩石的单轴抗压强度和弹性模量有较大影响,岩石的单轴抗压强度和弹性模量均与计算孔隙率、角度参数呈负相关,与构造参数呈正相关,与其余因素相关性较弱;随着模型孔隙率的增加,气孔杏仁状玄武岩应力-应变曲线中塑性应变占比随之增加,破坏模式由单剪切破坏面、多剪切破坏面转为局部粉碎状破坏,岩石由脆性破坏逐渐转为延性破坏,5%和12.5%可近似作为强脆性―脆性―延性转换的临界孔隙率;建立的损伤统计本构方程能够根据初始孔隙特征较好地预测气孔杏仁状玄武岩的力学行为,对于玄武岩地层中多孔岩石力学性质的确定具有重要意义。

The study focuses on investigating the influence of initial pores on the mechanical behavior of vesicular amygdaloidal basalt using a stochastic three-dimensional modeling method.The proposed modeling method considers calculated porosity,volume parameters,shape parameters,angle parameters,and structural parameters.Subsequently,five-factor and five-level orthogonal numerical simulations under uniaxial compression are conducted to analyze stress‒strain curves,damage modes,and failure characteristics.The calculated porosity,angle parameters,and structural parameters are found to strongly influence the uniaxial compressive strength(UCS)and elastic modulus of the rock.Specifically,the UCS and elastic modulus exhibit negative correlations with calculated porosity and angular parameters,while showing positive correlations with structural parameters.Weak correlations are observed with the remaining factors.The percentage of plastic strain in the stress‒strain curve of vesicular amygdaloidal basalt is noted to increase with increasing model porosity.The damage mode shifts from a single-shear surface,multiple-shear surface to local crush damage.Additionally,the rock transitioned from brittle to ductile failure.It is identified that a porosity of 5%and 12.5%can be approximated as critical values for the strong brittle‒brittle‒ductile transition.The established damage statistical constitutive equation is found to better predict the mechanical behavior of vesicular amygdaloidal basalt based on the initial pore.This suggests the potential importance of determining the mechanical properties of porous rocks in basaltic formations.