基于细观试验和离散元法的盐岩力学特性

Mechanical characteristics of salt rock based on mesoscopic tests and discrete element method

当前盐岩的宏观力学模型通常是唯象模型,不能很好地解释盐岩受力变形破坏的真正物理基础。盐岩是由于化学沉积而形成的矿物集合体,是一种主要由NaCl和少量杂质组成的多晶体,其变形机制主要由晶粒与晶界的力学特性控制。通过扫描电镜(SEM),获得盐岩晶粒的微细观结构特征,采用分子动力学方法和纳米压痕技术,确定盐岩晶粒和晶界的微细观力学参数;将盐岩晶粒作为块体,基于Voronoi多边形技术,建立盐岩的微细观数值模型;利用离散元方法,对盐岩试件在单轴压缩和直剪条件下的宏观力学行为进行了数值模拟。数值模拟结果与宏观力学试验结果吻合度高,表明基于盐岩微细观晶粒结构特征并结合离散元数值模拟的方法能够较好地研究盐岩的宏观力学性能及其材料物理基础。

The current macro-mechanical models of salt rock are usually phenomenological models, which cannot fully explain the true physical mechanism of mechanical deformation and failure of salt rock. Salt rock is a polycrystalline aggregate, which mainly consists of Na Cl and a few amounts of impurities formed in the geological lithification process. Its deformation mechanism is largely controlled by mechanical properties of the grain and grain boundary. The microstructure of the grain in salt rock was obtained by scanning electron microscopy（SEM）, and the micro/meso mechanical parameters of the grain and grain boundary were determined by molecular dynamics（MD） and nanoindentation technologies. Based on the numerical Voronoi polygon technology, a microscopic numerical model of salt rock was established by regarding grains of salt rock as deformable blocks. The discrete element method（DEM） was adopted to perform numerical simulation on the macroscopic behaviour of salt rock specimens under uniaxial compression and direct shear. Numerical results are in good agreement with macro-mechanical experimental results, which indicates that the method proposed on the micro/meso grains of salt rock and the DEM can describe macroscopic mechanical properties well based on physical microstructure of salt rock.