考虑矿物细观结构的岩石数字化模型构建及其应用

Construction and application of rock digital model considering mineral meso-structure

为更好地从矿物细观结构层面揭示岩石破裂机制,综合采用岩石偏光显微分析、CT技术和数字图像处理技术,构建能够反映岩石实际矿物成分、含量和空间分布等细观结构特征的岩石数字化模型。数值模拟和物理实验结果表明,该模型与真实岩石实际破裂过程具有较好的一致性,能够模拟出岩石变形破坏过程不同类型矿物断裂时裂纹萌生位置、扩展方式及产生机制等细观破裂行为,实现岩石破裂过程裂纹扩展方式(穿晶、沿晶)及其力学机制(张拉、剪切)的判别与定量分析。统计分析发现,裂纹扩展方式与矿物晶体力学属性强弱有关,在强矿物晶质体处以沿晶方式进行扩展,在弱矿物晶质体处以"沿晶+穿晶"的组合方式进行扩展。此外,裂纹扩展也受其产生的力学机制影响,微破裂稳定发展阶段产生的张拉裂纹,在强矿物晶体处以沿晶方式扩展,形成晶间张拉裂纹,在弱矿物晶体处以穿晶方式扩展,形成晶内张拉裂纹;非稳定破裂发展阶段和峰后破坏阶段产生的剪切裂纹,在强、弱矿物晶质体处均以沿晶方式扩展,形成晶间剪切裂纹。从裂纹网络形成方式来看,强、弱矿物晶质体分布较为集中时,形成主干式的裂纹网络,当强、弱矿物晶质体呈离散式分布时,形成网状分布的裂纹网络。

To better reveal the mechanism of rock fracture from the perspective of mineral meso-structure,a digital model of rock is constructed based on polarizing microscopy,computed tomography(CT)technology and digital image processing(DIP)technology,and the meso-structural characteristics of rock,such as actual mineral composition,content and spatial distribution,can be reflected through it.By comparing the results of numerical simulation experiments and physical experiments,it is found that the fracture process of the model is basically consistent with that of the real rock.The meso-fracture behavior of rock during deformation and failure,such as the initiation location,extended mode and generation mechanism of fractures in different types of mineral fractures,can be simulated.The modes of rock fracture propagation,such as transgranular and intergranular,and the types of failure,such as tensile and shear,can also be identified and quantitatively analyzed.It is found that the crack propagation mode is related to the strength of mechanical properties of mineral crystals.Specifically,the expansion mode at the strong mineral crystal is intergranular,and the expansion mode at the weak mineral crystal is intergranular and transgranular.In addition,the propagation mode of crack is also related to its mechanical mechanism.The tensile cracks,which generated in the stable development stage of micro fracture,whose propagation mode is intergranular at the strong mineral crystal,and the crack type is intergranular tensile crack.But the propagation mode at weak mineral crystal is transgranular,the crack type is intragranular tension crack.The shear cracks,which produced in the unstable fracture development stage and the post-peak failure stage,whose propagation mode at both strong and weak mineral crystals is intergranular,and the crack type is intergranular shear crack.From the perspective of crack network formation,when the distribution of strong and weak mineral crystals is relatively concentrated,a backbone crack network is formed.When the distribution of strong and weak mineral crystals is discrete,a network crack network is formed.