深部冻结软岩宏细微观蠕变损伤统一本构模型及其应用研究

With the mining development of coal resource in western China, most of shafts cuts through the cretaceous strata. The cretaceous strata presents several characteristics,such as the short time of diagenesis, weak cementation, low strength, and rich water. In order to explore stability mechanism of frozen wall at the cretaceous strata, and to develop the fundamental theory of freezing sinking shaft, the research on the coupling mechanisms of creep and damage are carried out by employing the method of macro-meso-micro incorporation under unloading condition. This project is concentrated on the following aspects: The CT scanning and acoustic emission experiments of frozen soft rocks are carried out under unloading creep process, and the relationship between meso-micro damage evolution characteristic and macro mechanics are studied. The research on the unloading creep characteristic of frozen soft rock is carried out, and the damage coupled unified macro-meso-micro creep constitutive model for frozen soft rock in deep shaft is establised based on the the hypothesis of damage energy equivalence. In order to describe the deformation behavior of frozen soft rock under complex stress state, the constitutive model is extended to the complex state by the method of transformation of stress space, and a stability analysis model of frozen wall is established. The research has important significance in exploring the deformation and failure mechanisms of frozen soft rock walls in western region, and could provide the theoretical basis for the optimization design and improvement of supporting method.

随着我国煤炭开采不断向西部地区发展，井筒穿越地层往往遇到大量白垩系软岩地层，该地层具有成岩晚、胶结弱、强度低、富含水等特点。为揭示深部白垩系软岩冻结壁稳定性力学机制，发展和完善深部冻结法凿井基础理论，本项目拟采用宏、细微观相结合的方法，研究开挖卸荷作用下冻结软岩蠕变损伤变形破坏机理。具体内容包括：开展卸荷蠕变冻结软岩的CT扫描和声发射试验，定量研究深部冻结软岩的细微观损伤演化与宏观力学行为之间的联系，建立符合实际的损伤演化方程；研究深部冻结软岩的卸荷蠕变特征，基于损伤能量等效性假设，构建卸荷蠕变条件下冻结软岩的宏细微观蠕变损伤耦合的统一本构关系；采用应力空间变换的方法将本构关系拓展到复杂应力状态，建立深部软岩冻结壁稳定性分析力学模型。通过开展本研究，对于揭示西部地区立井软岩冻结壁的变形破坏机理具有重要意义，并为冻结壁的优化设计与支护方式的改进提供理论依据。

我国西部地区矿井穿越地层多以白垩系、侏罗纪软岩地层为主，其属软弱类岩层，亲水性强、遇水后强度软化，容易导致井筒透水等事故。为揭示软岩地层井筒冻结壁变形破坏的机制，拟采用宏、细微观相结合的方法，研究软岩地层的冻结机制与变形破坏的力学行为，主要研究内容包括：.（1）研究了冻结软岩的物理力学特性，掌握了西部地区软岩地层冻结的工程物理力学参数，为探究冻结软岩热力学特征与冻结壁稳定性计算分析提供依据。.（2）开展了冻结软岩的核磁共振微观结构特征研究，分析了岩石的孔隙结构特征和冻结特征曲线，对比了不同地层岩石的孔隙分形维数，从微观层面揭示了西部地区岩层孔隙结构分布及未冻水含量随温度的变化规律。.（3）基于XRD、SEM、CT扫描等细微观实验，获取了岩石内部的矿物组成及细微观孔裂隙结构特征，采用改进的K-means聚类算法对非均质岩石细微观孔裂隙结构真实重构，获得孔裂隙细微观结构分布情况，为岩体损伤演化定量表征提供了方法。.（4）研究了卸载路径下岩石的宏观力学行为与细微观损伤演化特征，分析了卸载路径下损伤演化、能量的积累释放规律，提出了损伤裂隙指数计算式，建立了复杂应力空间的屈服破坏本构关系。.（5）研究了卸载路径冻结软岩粘弹塑性蠕变损伤演化规律，建立了冻结软岩宏微观结合的蠕变损伤统一本构关系，利用离散元模拟了卸载路径下冻结软岩蠕变损伤变形破坏规律，揭示了冻结软岩开挖卸荷变形破坏的宏微观蠕变损伤机制。.（6）探究了岩石与裂隙界面处的Stokes-Darcy耦合机制，构建渗流作用下的无充填裂隙岩体流-热耦合模型，开展了裂隙岩体冻结数值模拟，分析了裂隙开度、渗流速度以及冻结管间距对裂隙岩体冻结温度场的影响规律。.（7）基于热力学基本定律，推导了动态水冰相变平衡方程，利用VG模型、Young–Laplace方程以及动态水冰相变平衡关系，建立了人工冻结冻结壁水热动态耦合模型，并结合大型模型试验与现场结果验证了模型合理性。