综合考虑细观缺陷和矿物夹杂的岩石本构模型及数值方法研究

It is currently complex to study the macroscopic behavior of rock materials by taking into account the microdefects such as microcracks and micro-voids and the mineral inclusions at the same time. This project intends to develop a multi-scale damage constitutive model as well as a numerical method for rock materials from the microscopic to the macroscopic level. It aims to further explore the effect of microcracks and micro-voids related damage evolution and the local mechanical properties of the mineral inclusion interface on the macroscopic mechanical behavior of the rock materials. Based on the macroscopic and microscopic mechanical experiments in the laboratory, the influences of initiation, growth and coalescence of microcracks and micro-voids, and the proportion and distribution of mineral inclusions as well as their interfaces under different stress conditions on the macroscopic mechanical behaviors of rock materials will be analyzed from the view of micromechanics. Considering the mutual influences of micro-defects and mineral inclusions, a micromechanical damage constitutive model based on the micromechanims will be proposed based on the damage evolution laws for micro-defects and the failure criteria for mineral inclusion interfaces. Taking advantage of the fast Fourier transform based method that does not require meshing for complex microstructures, a numerical model will be developed by considering microstructure evolution with the large number of microcracks, micro-voids, and mineral inclusions at the same time. The numerical method will be optimized and the calculation will be fulfilled with the homogenization theory to effectively predict the macroscopic mechanical behaviors of rock materials. The results can further deepen the rock constitutive theory based on micromechanical theory and provide a reliable theoretical basis for studying the nonlinear mechanical behavior of rock materials.

综合考虑微裂纹、微孔洞等细观缺陷和矿物夹杂对岩石材料宏观力学行为的影响是目前研究的难点。本项目拟开展从细观到宏观的岩石多尺度损伤本构模型和数值方法研究，深入探究微裂纹、微孔洞的损伤演化和矿物夹杂界面的局部力学特性对岩石宏观力学行为的影响。结合室内宏细观力学实验，从细观机理上分析不同受力情况下微裂纹和微孔洞萌生、扩展和融合及矿物组分的比例、分布和界面行为对宏观力学行为的影响规律和力学机理。综合考虑细观缺陷和矿物夹杂的相互影响，提出针对细观缺陷的损伤演化方程和矿物夹杂界面的破坏准则，建立基于细观力学机理的损伤本构模型。采用无需对复杂细观结构划分网格的快速傅立叶变换方法，建立同时存在大量微裂纹、微孔洞和矿物夹杂的细观结构及演化的数值模型，优化数值计算方法，并结合均匀化理论计算和预测岩石的宏观力学行为。项目成果可进一步深化基于细观力学的岩石本构理论，为研究岩石材料非线性力学行为提供可靠的理论基础。

岩石内部的细观缺陷和矿物夹杂等细观结构特征对岩石材料宏观非线性力学行为和破坏过程有着十分重要的影响。本项目采用试验研究、理论分析与数值计算结合的方法，研究了岩石细观结构特征及其损伤演化对宏观非线性力学行为和破坏过程的影响。主要开展并取得了如下研究成果：(1)开展了一系列宏细观实验，分析了岩样的细观结构特征，包括矿物组分、比例、大小及分布和微裂纹密度及分布等非均质性特征，获得了岩石的强度、变形等宏观力学参数和应力应变曲线，建立了岩石细观结构特征与宏观力学行为之间的内在联系。(2)利用数字图像处理技术表征了岩石细观结构特征和加载中的微裂纹演化过程，根据细观结构特征和不同矿物的局部力学特性，建立了能合理描述细观结构特征和损伤机理的细观损伤本构模型。(3)结合FFT数值方法和数字图像处理技术，建立了能直接利用岩石图像生成真实细观结构数值模型的DIP-FFT数值计算方法，计算并预测了岩石的强度、变形和应力应变曲线等宏观力学行为，模拟了矿物夹杂引起的应力分布规律、微裂纹演化过程和矿物颗粒界面损伤破坏等细观力学行为，分析了矿物夹杂和微裂纹演化等细观结构特征对宏观非线性力学行为和破坏过程的影响规律。研究成果有助于深化基于细观力学的岩石损伤本构理论，为研究岩石材料非线性力学行为提供理论基础。