泥质板岩横观各向同性弹塑性耦合变形与强度准则的试验研究

【作者】 张久长；

【导师】 方理刚；

【作者基本信息】 中南大学 ， 岩土工程， 2010， 硕士

【摘要】 岩石在微观、细观和宏观尺度上都表现出各向异性。微观层次上,晶体形成矿物集合体的排列方式会引起岩石细观矿物集合体的各向异性。在细观层次上,岩石组分和矿物集合体的结合方式将对岩石宏观力学各向异性产生极大的影响。为此,本文针对含有明显层理状结构的泥质板岩,开展了微观矿物成分、细观岩石结构和宏观力学性质的试验研究。(1)在微观尺度上,借助XRD试验,分析出泥质板岩含有石英、高岭石、白云母和斜绿泥石等矿物成分,并指出这些矿物的晶体以一定方式排列时将对细观矿物集合体的各向异性产生影响。(2)在细观尺度上,通过扫描电镜试验,获得了泥质板岩细观结构的显微照片。分析发现,泥质板岩的结构以变晶结构为主,包含了由石英晶体形成的颗粒状矿物集合体和由高岭石、白云母和斜绿泥石形成的片状矿物集合体,但以片状集合体为主。这些矿物集合体在重力作用下以水平方向为优势方向排列,从而决定了泥质板岩具有横观各向同性的力学性质。(3)在宏观尺度上,通过泥质板岩不同倾角岩样的单轴压缩和三轴循环加卸载试验,研究了泥质板岩的变形性质和强度行为。发现泥质板岩的变形存在明显的弹塑性耦合现象。不同加载角度下的视弹性模量随塑性应变的增大而呈指数规律衰减。采用数据拟合的方法获得了视弹性模量与塑性应变间的经验函数关系。通过对循环加卸载应力应变曲线的分析,将塑性应变、弹性应变和弹塑性耦合应变从总应变中分离出来。加载初期,泥质板岩以塑性变形为主,随着加载和总应变的增大,塑性应变在总应变中所占的比重逐渐降低,而弹性应变和弹塑性耦合应变的比重却在增大。泥质板岩的抗压强度与围压和加载方向有关。强度的各向异性受围压影响显著,随着围压的增大,强度各向异性降低。提出泥质板岩的粘聚力与摩擦系数随角度变化的经验Mohr-Coulomb强度准则。通过数据拟合,得到了准则中相关参数的值,并在σ1、β和σ3组成的三维空间中绘制了这个准则的强度面。更多还原

【Abstract】 Anisotropy of rocks can occur at the micro, meso and macro scales in all. The crystals of minerals have some degree effects on the anisotropy of rocks. The effects mainly depend on the arrangement of mineral aggregates which were formed by the collection of the mineral crystals. At the mesoscopic level, the combining form of components and mineral aggregates of rocks have great effects on the anisotropy of rock mechanics behaviorAnalysis of mineral micro-components and meso structure, experiments of macroscopic mechanical properties of argillite with a clear stratification structure were launched in this paper.(1) At the micro scale, the components of argillite:quartz, kaolinite, muscovite and clinochlore were analyzed by XRD. Arrangements of the crystals of these minerals have effects on the anisotropy of mineral aggregates was pointed out.(2) At the mesoscopic scale, by scanning electron microscopy experiment, the micrographs of microscopic structure of the argillite were photographed. Analysis showed that the main type of structure in argillite was crystalloblastic texture, which contains granular mineral aggregates made of quartz crystal, and schistose mineral aggregates made of the crystals of kaolinite, muscovite and clinochlore. But the main component was schistose mineral aggregates. Under gravity, these mineral aggregates arranged to the dominant horizontal direction, and this kind of arrangement determined the argillite with transversely isotropic mechanical properties.(3) At the macro scale, experiments of uniaxial compression and triaxial cyclic loading tests of argillite rock samples with different angles were launched. Studied the deformation and strength properties of argillite, and found the obvious existence of elastoplastic coupling deformation. Under different loading angles, the apparent elastic moduli decayed exponentially with the increase of plastic strain. Obtained the relation of experience function between apparent elastic moduli and plastic strain by fitting method. Through the analysis of cyclic loading and unloading stress-strain curve, plastic strain, elastic strain and elastoplastic coupling strain were separated from the total strain. At the beginning of loading, the main deformation was plastic. With the increasing of load and total strain, the proportion of plastic strain in total strain gradually decreased, while the proportions of elastic strain and elastoplastic coupling strain increased. The compressive strength of argillite varied with the difference of confining pressures and loading directions. Strength anisotropy of argillite significantly affected by the confining pressures, and with the gradual increasing of confining pressures, the degree of strength anisotropy reduced. Proposed anisotropic empirical Mohr-Coulomb strength criterion with cohesion and the friction coefficient changing with loading directions. Through the data fitting method, obtained the values of relevant parameters, and graphed the strength surface of this criterion in three-dimensional space composed ofσ1,βandσ3.更多还原