摘要： 古龙页岩显著的层理构造与强各向异性特征,给深部工程的岩石力学响应预测带来了巨大挑战。针对传统数值方法难以兼顾基质与层理弱面非连续力学响应的难题,本文提出了一种适用于古龙页岩的精细化离散元建模方法。该方法构建了基于线性平行黏结与平滑节理的二元耦合本构模型,通过引入“基质-层理独立解耦”参数标定策略,有效消除了传统建模中因参数强度倒置引发的非物理延性变形问题。基于该基准模型,系统开展了不同层理倾角下的单轴压缩数值试验,深入揭示了宏观各向异性的细观物理机制。研究表明：（1）模型客观复现了古龙页岩抗压强度呈“U型”变化的各向异性规律,揭示了破坏模式由基质张拉劈裂（θ = 0°和90°）向沿层理剪切滑移及压剪混合断裂（θ = 30°~60°）转化的力学机制;（2）细观损伤演化分析表明,在中间倾角区间（θ = 30°~60°）,微观剪切裂纹数量呈现爆发式增长并彻底反超张拉裂纹,其在空间上的局域化汇聚定量证实了弱面摩擦滑移的核心控制作用;（3）针对深部高围压与交变应力环境,探讨了该基准模型向三轴及循环加卸载工况拓展的物理边界,指出了引入非线性摩擦强化与微裂纹闭合滞后效应的升级演化路径。本研究建立的数值模型及微观机制认知,为深部各向异性页岩储层的力学参数预测与缝网模拟提供了理论支撑。

关键词: 古龙页岩, 离散元模型, 参数解耦标定, 微观损伤机理, 各向异性

Abstract: The distinct bedding structure and strong anisotropy of Gulong shale pose significant challenges to the prediction of rock mechanical responses in deep engineering. To address the limitations of traditional numerical methods in balancing the discontinuous mechanical behaviors of the rock matrix and bedding weak planes, a refined discrete element modeling approach suitable for Gulong shale is proposed. A binary coupled constitutive model based on the Linear Parallel Bond (PBM) and Smooth Joint (SJM) was constructed. By introducing an "independent decoupling" parameter calibration strategy for the matrix and bedding, the non-physical ductile deformation caused by parameter strength inversion in traditional modeling was effectively eliminated. Based on this benchmark model, numerical uniaxial compression tests under various bedding inclination angles were systematically conducted to reveal the microscopic physical mechanisms of macroscopic anisotropy. The results indicate that: (1) The model objectively reproduces the "U-shaped" strength anisotropy of Gulong shale and reveals the mechanical transition of failure modes from matrix tensile splitting (θ= 0°and 90°) to bedding shear slip and mixed compression-shear fracture (θ = 30°~60°). (2) Micro-damage evolution analysis demonstrates that in the intermediate inclination range (θ = 30°~60°), the number of microscopic shear cracks exhibits an explosive surge and completely surpasses that of tensile cracks. Their spatial localized convergence quantitatively confirms the core controlling role of weak plane frictional slip. (3) Targeting the deep environment with high confining pressure and alternating stress, the physical boundaries for extending this benchmark model to triaxial and cyclic loading conditions were discussed, and an upgrading path incorporating nonlinear friction strengthening and micro-crack closure hysteresis effects was pointed out. The numerical model and microscopic mechanisms established in this study provide reliable underlying theoretical support for mechanical parameter prediction and fracture network simulation in deep anisotropic shale reservoirs.

Key words: Gulong shale, discrete element model, parameter decoupling calibration, microscopic damage mechanism, anisotropy

中图分类号: 

• P618.13

• TE122