酸溶解作用下孔隙尺度岩石变形-损伤-破裂演化过程的直接数值模拟

The macroscopic failure of rocks during acid dissolution is the accumulation and growth of deformation, damage and fracture at the pore-scale to a certainty. Due to its complexity and the difficulty of its analytical solution, numerical simulation has become an important tool for studying this problem. This project is to propose a direct numerical simulation model which can be used to modeling the deformation, damage and fracture evolution processes of rocks at pore-scale during acid dissolution, and then to analysis rock failure law during acid dissolution. By applying model establishing, code programming, laboratory test and computational simulation, this project supposes to perform study on the following aspects: ① establishing a coupled PSM-IMB-LBM (i.e. PIL) model, this proposed model tracks the deformation and fracture of rocks by the particle simulation method (PSM), describes the fluid flow and mass transport by the lattice Boltzmann method (LBM), and realize the solid-fluid coupling by the immersed moving boundary method (IMB); ② developing the corresponding program using Fortran, verifying and validating the program through benchmark tests and experimental results; ③ modeling deformation, damage and fracture evolution processes of rocks at pore-scale during acid dissolution using the proposed PIL coupling model, and discussing damage and fracture evolvement laws of rocks. The outcome of this project is not only of theoretical fundamental to analysis the mesoscopic fracture mechanism of rocks during acid dissolution, but also of certain practical application to propose an accurate constitutive model for modeling upscale problems.

酸溶解作用下岩石的宏观破坏是孔隙尺度上变形、损伤、破裂累积与发展的结果。鉴于这一问题的复杂性和解析求解难度，数值模拟成为该问题的重要研究手段。本研究将构建可对酸溶解作用下孔隙尺度岩石变形-损伤-破裂演化过程进行直接模拟的数值模型，用以研究酸溶解作用下岩石破坏规律。拟采用数值建模、程序编制、室内试验和计算模拟等手段，研究内容为：①构建PIL（即PSM-IMB-LBM）耦合模型，该模型采用颗粒法（PSM）描述岩石变形破裂，格子Boltzmann方法（LBM）描述流体流动和化学物质输运，浸入移动边界法（IMB）实现流固耦合；②基于Fortran编写PIL耦合模型的计算程序，采用标准考题和室内试验进行对比验证；③对酸溶解作用下孔隙尺度岩石变形-损伤-破裂演化过程进行直接数值模拟，探讨岩石损伤与破裂规律。研究成果不仅可深入认识酸溶解作用下岩石细观破裂机理，还可为更高尺度上的模拟提供可靠的本构模型。

酸溶解作用下岩石破裂过程是岩石破裂机制研究的难点，也是石油开采和环境岩土工程等领域的基础课题之一，具有十分重要的科学理论意义和工程实用价值。本项目以岩石为研究对象，采用试验研究、模型构建、程序编制和数值模拟相结合的方法，对不同条件下岩石和煤岩组合体变形-损伤-破裂演化过程进行了研究。主要成果如下：（1）构建了PIL（即PSM-IMB-LBM）耦合模型，该模型采用颗粒法（PSM）描述岩石颗粒的运动和碰撞，格子Boltzmann方法（LBM）描述流体流动和化学物质输运，浸入移动边界法（IMB）实现运动颗粒与流体界面上的非滑移边界和Dirichlet浓度边界；（2）基于Fortran语言编写了PIL耦合模型的计算程序，该模型可对酸溶解作用下孔隙尺度岩石颗粒运动-流体流动-化学物质输运过程进行直接数值模拟；（3）基于颗粒法，对循环加载、不同加载波形和高应变率下岩石和煤岩组合体变形-损伤-破裂演化过程进行了数值模拟，探讨了岩石和煤岩组合体的损伤与破裂规律。本项目研究期内共发表标注项目编号的论文6篇，其中SCI收录论文4篇，EI收录论文1篇。