岩石破裂过程的统计损伤模型及裂隙岩体渐进破坏数值模拟

发布时间：2018-12-16 01:18

【摘要】：传统岩石力学建立在唯象理论基础上,不能完全解释岩石破坏的机理,也不能再现岩石的非线性力学特征；建立在传统岩石力学理论基础上的有限元方法也不能合理地模拟岩石中的裂纹扩展等与广义时间相关的渐进破坏过程。随着岩土工程向更高、更深方向发展,一些新的非线性的力学现象的研究不可避免,岩石力学的发展出现前所未有的挑战。从岩石细观机制出发,综合细观力学、断裂力学、损伤力学以及统计力学的研究成果,重新审视岩石的本构关系,显得十分必要。本文从岩石显微观察结果出发,推导了微裂纹在持续张拉加载条件下的裂纹扩展长度与远场应力增量的关系,将其引入多层次非平衡统计理论,以断裂概率为损伤变量,将岩石细观力学机制与宏观损伤过程统一起来,建立了跨尺度的岩石张拉损伤演化本构方程。利用滑动裂纹模型,推导了压缩条件下翼裂纹扩展的等效远场拉应力,将压缩条件下的损伤演化统一到张拉损伤演化方程,同时也获得了材料劈裂破坏判据。随后对本文得出的本构关系内禀的尺度参数及岩石材料的强度尺寸效应律进行了研究,认为本文获得的本构方程具备岩石材料基本的宏观力学特征；研究了初始损伤对应力应变曲线的影响,得出本文推广模型与考虑材料初始损伤对应力应变曲线的影响效果是一致的结论。为了建立岩石渐进破坏的计算方法,将损伤演化方程嵌入弥散裂缝模型来建立满足断裂能守恒的单元破坏准则,研究并证实了双标量损伤模型与单标量损伤模型在本文的研究中是等效的,从而验证了张拉损伤与剪切损伤的同步性,也对弹脆性模型实现裂纹扩展的方法进行了合理解释。为考虑初始裂隙的力学特征,建立了隐含贯通粗糙节理的等效裂缝模型,用于计算工程岩体中本已存在的节理裂隙的影响,以避免实体模型的建模困难。最后在以上研究成果的基础上,通过实例建立了断续节理岩体等效力学参数的测定方法,通过对断续节理岩体进行加卸载数值试验,研究其破坏模式、强度条件及强度参数。研究结果显示,本文方法获得的工程岩体的等效力学参数比工程岩体分类的传统方法获得的强度参数要高30%-50%。
[Abstract]:The traditional rock mechanics is based on phenomenological theory, which can not fully explain the failure mechanism of rock, nor can it reproduce the nonlinear mechanical characteristics of rock. The finite element method, which is based on the traditional rock mechanics theory, can not reasonably simulate the progressive failure process such as crack propagation and generalized time dependent in rock. With the development of geotechnical engineering towards higher and deeper direction, the study of some new nonlinear mechanical phenomena is inevitable, and the development of rock mechanics presents unprecedented challenges. It is necessary to re-examine the constitutive relations of rocks from the point of view of meso-mechanics, fracture mechanics, damage mechanics and statistical mechanics. Based on the microscopic observation of rock, the relationship between the crack propagation length and the far field stress increment under the condition of continuous tensile loading is deduced, and the fracture probability is taken as the damage variable by introducing it into the multilevel non-equilibrium statistical theory. By unifying the mesomechanical mechanism of rock with the macroscopic damage process, the constitutive equation of rock tensile damage evolution across scales is established. Using the sliding crack model, the equivalent far-field tensile stress of wing crack propagation under compression condition is derived. The damage evolution under compression condition is unified to the tensional damage evolution equation, and the splitting failure criterion is also obtained. Then the intrinsic scale parameters of the constitutive relation and the strength and size effect law of rock material are studied. The constitutive equation obtained in this paper has the basic macroscopic mechanical characteristics of rock material. The effect of initial damage on stress-strain curve is studied. It is concluded that the generalized model is consistent with the effect of considering material initial damage on stress-strain curve. In order to establish the calculation method of progressive failure of rock, the damage evolution equation is embedded into the dispersive fracture model to establish the element failure criterion which satisfies the conservation of fracture energy. It is proved that the double scalar damage model and the single scalar damage model are equivalent in this paper, which verifies the synchronism of tensile damage and shear damage, and gives a reasonable explanation for the method of crack propagation in elastic brittle model. In order to consider the mechanical characteristics of the initial fracture, an equivalent fracture model is established, which can be used to calculate the influence of the existing joints and fractures in engineering rock mass, so as to avoid the difficulty of modeling the solid model. Finally, on the basis of the above research results, the method of measuring the equivalent mechanical parameters of jointed rock mass is established through an example, and the failure mode, strength condition and strength parameters of intermittent jointed rock mass are studied by means of loading and unloading numerical test of intermittent jointed rock mass. The results show that the equivalent mechanical parameters of engineering rock mass obtained by this method are 30 to 50 higher than those obtained by traditional method of engineering rock mass classification.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU45

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