【作者】 陈芳；

【导师】 张强勇；

【作者基本信息】 山东大学 ， 岩土工程， 2012， 博士

【摘要】 随着我国经济建设的快速发展及水利水电资源不断的开发利用,岩石工程项目不仅越来越多,工程开挖规模也越来越大,由此引出的围岩稳定性问题日益突显。岩体工程稳定性评价的关键在于需要深入了解工程岩体的流变力学特性及其相应的岩体力学参数取值方法,并在理论上深入地对工程岩体长期运行稳定性进行分析,其中的关键就是需要分析得出材料力学参数随应力和时间不断弱化的时效演化模型,特别是建立考虑时间效应的流变强度时效模型。本文以大岗山水电站坝区的硬脆性辉绿岩为研究对象,基于对硬脆性辉绿岩在不同应力状态下的室内三轴流变试验结果,确定出了硬脆性岩体的力学参数随时间和应力水平的变化规律,继而建立了硬脆性岩体的流变时效强度模型,并将其应用到了实际工程的数值分析中。本文的研究工作主要是以下几个方面：(1)采用全自动岩石三轴流变伺服仪开展了大岗山水电站坝区硬脆性辉绿岩的室内三轴流变力学特性试验,分别从轴向、侧向和体积变形等三个方面分析了不同围压、不同应力水平下硬脆性岩石变形随时间的变化规律,研究了硬脆性辉绿岩在三轴流变过程中的变形特性,探讨了岩石的等时应力～应变曲线特征、变形速率特征、蠕变对变形和强度的影响,分析了岩石的蠕变损伤阀值,并从细观和宏观力学两个方面解释了硬脆性辉绿岩的蠕变过程曲线,初步掌握了硬脆性辉绿岩流变特性的基本规律,明确了硬脆性岩石的流变破裂机理。(2)依据中水顾成都勘测设计研究院在坝区现场做的大型直剪试验和大型剪切蠕变试验的资料,研究了考虑加载历史影响的剪切蠕变变形规律和剪切蠕变速率特性,通过模型辨识和参数反演得到了硬脆性辉绿岩体的剪切蠕变参数。分别采用等时应力～应变曲线法、非稳定蠕变判别法和稳态蠕变速率法计算获得了坝区硬脆性辉绿岩体的长期剪切流变强度,并将各结果进行了对比分析,最终确定出了硬脆性辉绿岩体的长期剪切流变强度。将岩体的长期抗剪指标与瞬时抗剪指标进行了对比,得到了岩体在长期恒定荷载作用下强度参数的衰减百分率。(3)通过分析硬脆性辉绿岩蠕变过程中力学参数的弱化规律,建立了岩体弹性模量E、粘聚力C、内摩擦角φ与应力及时间的时效演化模型,从定量的角度描述了硬脆性辉绿岩在蠕变过程中的损伤演化过程,并基于蠕变破坏时岩体的强度变化验证了时效演化模型的合理性与正确性。(4)基于硬脆性辉绿岩单轴、三轴压缩试验的结果,从变形、强度、能量及破坏等不同角度对硬脆性辉绿岩在不同应力状态下的变形特征、强度特征及能量耗散特征等进行了较为系统的分析,获得了硬脆性辉绿岩的基本力学特性和变形破坏规律。利用裂纹应变模型,明确了岩体内部裂纹发展演化的规律以及强度破坏机理。(5)将硬脆性岩体力学参数的时效演化模型引入到八面体应变能强度模型中,建立硬脆性岩体的流变强度时效模型,并通过三轴试验结果验证了该流变时效强度模型的正确性。(6)通过C++与Fish编程对有限差分软件Flac3D进行二次开发,实现力学参数时效演化模型的程序化和强度准则的非线性化,并将其应用于大岗山水电站坝区边坡的长期稳定性分析中,系统地对位移矢量场、应力矢量场以及塑性屈服区等进行综合分析,总结了围岩体力学响应的时空演化规律和特征,对坝区岩体的施工开挖和长期运行稳定性提出合理的工程建议。这些问题的研究为下一步渗流对岩石强度的影响的研究提供了基础信息和理论依据。更多还原

【Abstract】 With the increasing development of China’s economic construction and water conservancy and hydropower resources development, not only the number of rock projects are rising, but also the excavation scope are extending, which leads to highlight problems associated with the stability of rock mass. The key factor with respect to rock engineering stability evaluation is to acquire comprehensive and deep perception of rheological and mechanical characteristics and the corresponding determination of mechanical parameters in rock engineering. Moreover, in-depth analysis of long-term operational stability of engineering rock is required. Therefore, discovering the functional relationship of weakened material parameters affected by stress and time variation, especially proposing rheological strength damage model concerned with the time effect, plays a crucial role in these topics. In this thesis, based on precious literatures, large-scale in situ shear creep test results in Dagangshan Hydropower Station Dam, and triaxial laboratory tests on rheological properties of fragile diabase, variation principles of mechanical parameters of diabase under different time and stress conditions, were determined. Then, a rheological strength damage model was proposed, and its verification was proved by situ engineering. The main contents of this thesis were listed as following:1. With the help of automatic triaxial rock rheology servo instrument, triaxial laboratory tests on rheological properties of fragile diabase in Dagangshan Hydropower Station Dam were carried out. The variation mechanism of brittle rock over time under different confining pressure and stress levels was discussed, regarding axial, lateral and volumetric deformation respectively. Meanwhile, deformation characteristics of diabase under triaxial rheology, stress-strain curves characteristics, strain rate characteristics, and influence of creep on the deformation and strength of brittle rock, were studied. The creep damage threshold of diabase was analysed as well. This thesis demonstrates the creep process curve of diabase from both micro-mechanics and macro-mechanics views. Initially basic principle of the diabase rheological properties was acquired, and rheological fracture mechanism of brittle rock was indicated.2. Based on the shear creep test results in Dagangshan Hydropower Station Dam, the thesis discussed shear creep deformation laws concerning load history, distinguished the shear creep models of diabase, and obtained the shear creep parameters of the diabase in the dam site by inversion. By utilizing the isochronous stress-strain curves method, non-steady creep discriminance, steady creep velocity method respectively, and long-term shear rheological strength of the diabase were obtained. After that, the different results were compared, ensued with the determination of long-term shear rheological strength of the diabase. Through comparisons of long-term shear strength and transient shear strength, attenuation percentage of the strength parameters of rock mass under long-term constant loads was obtained.3. The thesis determined the mechanical parameters of diabase in creep process, analyzed the weakening law of the mechanical parameters of rock mass, and established the damage evolution equations (i.e. the formula of elastic modulus, cohesion and friction angle, in accordance with stress and time of rock mass). The process of creep damage evolution of diabase was described from a quantitative view, and the functional relation was certificated by the strength variation of rock creep damage.4. Based on the results of uniaxial compression tests, triaxial compression tests, and load-unload tests, systematic analysis on the diabase deformation characteristics, strength characteristics and energy dissipation characteristics under different stress states was made from the different views regarding deformation, strength, energy, and damage, and the instantaneous mechanical properties and deformation damage law of the diabase were gained. With the help of fracture strain model, the internal propagation principle of rock and intensity failure mechanism was identified.5. The mechanical parameter variations of diabase were introduced to the strength formula, and the model that could reflect the aging rheological damage intensity of diabase was established.6. Secondary development of the finite difference software Flac3D was processed through programming of C++and FISH language, which achieved programming of rheological aging evolution model, and then it was applied to the study of long-term stability of the Dagangshan Hydropower Station Dam slopes. Displacement vector fields, stress vector fields and distributions of yield areas were analyzed comprehensively and systematically. Eventually space-time evolution principle and characteristics of mechanical response of rock mass were summarized, while sensible engineering suggestions on the excavation and long-term stability of rock mass in the dam regions were given. In conclusion, the research on these issues will certainly make contribution to the further seepage influence study of rock mass, providing basic information and theoretical foundation.更多还原