深埋硬岩优势结构与卸荷破裂协同时变机制研究

To solve the bottleneck problem that the study on time effect is scare and the cognition about time-varying mechanism is not clear of preferred geological structures of deep hard rock, the hard rock with three kinds of preferred structures is taken as the research object, sparse structural plane, fault fracture zone and thin and medium thick layer interbed, developing in the field of second stage major scientific research platform field area of Jinping deep underground laboratory, the study will establish new creep test considering the effect of unloading path, and reveal the unloading time effect regularity and formation mechanism of two time-dependent mechanical unit hard rock structure plane and new fracture surface. Coupling discrete fracture network and clumped-particle model, combined with parallel-bonded stress corrosion model and structure plane time-dependent smooth-joint model of hard rock, the study will establish the modified synthetic rock mass (MRSM) model which unified characterization and comprehensive simulation of time effect of preferred structure and failure evolvement of hard rock. Based on the MSRM inversion analysis of multiple time-dependent monitoring information, the study will mainly reveal the synergistic effect and coupling effect mechanism between the time effect of preferred structure and time-dependent failure of complete hard rock, build the "time-dependent criterion" of hard rock with three dominant structures, identify the key control factors, and quantify the difference and anisotropy of the time effect. This study can provide a new way to study the time effect of hard rock, more can provide a new theory and method for rockbursts hysteresis mechanism interpretation of deep engineering, evaluation of excavation damage zone and long-term stability analysis of surrounding rock.

针对深埋优势结构硬岩时效研究匮乏和时变机制认知不清的瓶颈问题，拟以锦屏深部地下实验室二期重大科研平台场区发育的含稀疏结构面（组）、断层破碎带和薄、中厚层互层的三类优势结构硬岩为研究对象，建立考虑卸荷路径效应的新蠕变试验方法，揭示硬岩结构面和新生破裂面两时效力学单元的卸荷时效规律与成因机制；耦合节理裂隙网络和颗粒簇模型，联合硬岩应力腐蚀模型和硬岩结构面时效光滑节理模型，建立将优势结构时效行为与硬岩破裂演化统一表征、综合模拟的改进合成岩体模型方法（MRSM）；基于多元时效监测信息的MSRM反演分析，重点揭示优势地质结构时变与完整硬岩时效破裂间的协同效应与耦合作用机理，构建三类优势结构硬岩的“时效准则”、识别其关键时效控制因素、量化其时效行为的差异性和各向异性。本研究可为硬岩时效研究开辟新途径，更可为深部工程岩爆滞后机理解译、开挖损伤区评估和围岩长期稳定性分析等提供新理论和方法。

针对高应力结构性硬岩的时效变形、破裂行为产生与控制机制认知匮乏及其数值分析方法欠缺严重制约了应力诱发时滞性岩爆灾害机制准确解译和风险可靠评估的瓶颈问题，本项目以三类优势结构硬岩（主要考虑含稀疏结构面（组）、断层破碎带和薄和中厚层互层大理岩）时间依赖变形和破裂行为为突破口，揭示多尺度岩体结构与构造对硬岩时效变形与破裂的控制作用。采用了室内试验模拟（如（真）三轴蠕变试验）、现场测试数据分析与挖掘（如钻孔孔内摄像、隧洞表面三维激光扫描与结构面摄影测量、原位长期力学行为监测试验，包括位移、锚杆应力以及破裂过程长期监测）、数值方法解译与反演（如粘结块体离散元与有限元-离散元耦合方法、岩体裂隙网格模型、结构面时效力学本构模型）等综合技术手段，从室内试验尺度研究了硬岩在复杂应力状态下蠕变变形规律与时效破裂演化行为；从深部地下实验室洞室尺度研究了优势结构硬岩的地质力学模型与几何表征以及应力场分布规律等，提出了三类优势结构硬岩发育区背斜构造地质力学模型与岩体三维裂隙网络模型构建方法，识别了优势结构硬岩发育区的地应力场分布特征与结构面统计规律。从理论与力学模型角度构建了基于过应力理论硬岩结构面弹塑粘塑性时效软化力学模型（EPVP本构模型），并提出了硬岩时效变形与时效破裂统一表征的BBM-EPVP数值方法，揭示了硬岩时效破裂与时效变形行为间协同效应与耦合作用机制；从数值分析与反演角度，采用有限元-离散元耦合方法（FDEM）研究了具有主控结构面组硬岩破裂行为，揭示了裂隙网络结构硬岩开挖后二次应力场分布规律及裂隙网络的控制作用。上述研究成果可为深部工程岩爆滞后机理解译、开挖损伤区评估和围岩长期稳定性分析等提供新理论和方法，可应用于川藏铁路隧道以及类似深部隧洞工程岩爆风险评估与支护设计，具有较高的应用前景和工程价值。