脆性岩石抗拉特性及其破裂机制的试验与细观模拟研究

发布时间：2018-05-25 04:01

本文选题：脆性岩石破裂机制 + FJM3D模型　；参考：《北京科技大学》2017年博士论文

【摘要】：脆性岩石破裂机制研究是深部岩石工程的基础科学问题。常见的脆性岩石破坏形式包括剥落、冲击地压、岩爆等,其危害轻则影响工程施工进度安排,重则造成设备人员伤亡重大损失,甚至可能会诱发工程失效,事关国家安全和国计民生。传统的试验方法不能探索脆性岩石内部破坏过程,强度准则不能有效解释脆性岩石破坏现象,经典离散元细观模型在分析脆性岩石破裂机制上存在一些显著缺陷。诸多的室内试验和现场原位试验表明,脆性岩石破坏中细观张拉裂纹扮演着主导角色。本文从室内试验及细观分析角度,研究脆性岩石抗拉特性,首先选取合适的细观模型,其次结合室内试验结果,分别就脆性岩石的三大特征、巴西抗拉强度和I型断裂韧度进行深入分析,探究了脆性岩石细观张拉破裂机制。主要研究工作和研究成果如下：(1)完整脆性岩石的室内试验结果呈现三大显著特征：高压拉比、大内摩擦角和强度包络线非线性,而经典黏结颗粒细观模型(Bonded-particle model)—标准BPM在匹配脆性岩石宏观力学性质时存在这三个显著缺陷。通过分析标准BPM的组成和本构关系以及标准BPM改进模型的特点,总结了造成这些显著缺陷的原因,提出采用新的黏结细观模型—平节理模型(3D flat-joint model, FJM3D)开展脆性岩石研究。(2)根据锦屏大理岩室内压缩和抗拉试验结果,结合FJM3D模型校核过程和参数敏感性分析结果,掌握了对脆性岩石三大特征起决定性作用的细观参数,并提出了一套能全面反映脆性岩石宏观力学性质的校核方法。(3)依据典型的巴西劈裂试验和Brisbane凝灰岩室内试验结果,借鉴多边形近似求圆周长的思想,提出采用FJM3D模型直接生成巴西圆盘细观模型,通过圆周分辨率控制圆周光滑度,解决了标准BPM存在的缺陷和传统圆盘建模方法造成的问题,通过参数敏感性分析掌握了影响巴西抗拉强度(BTS)的关键细观参数。(4)通过花岗岩人字形切槽巴西圆盘(Crack chevron notched Brazilian disc, CCNBD)试验,得出了试样尺寸和加载速率对Ⅰ型断裂韧度(K_(Ic))的影响规律。采用FJM3D模型和光滑节理模型(Smooth joint model, SJM)共同构建了CCNBD细观模型,结合矩张量理论,获得了该花岗岩声发射b值约为1.7242和声发射事件的频数与所包含的裂纹个数之间的关系。拟合多组细观模型计算结果,得出了K_(Ic)与黏结抗拉强度σ_b呈线性正相关,与晶粒直径平方根(Davg)~(1/2)呈指数正相关,与晶粒尺寸非均匀性平方根(dmax/dmin)~(1/2)呈指数负相关。(5)查阅国内外大量可获得的脆性岩石资料,理论上定性分析了抗拉强度(TS)、启裂应力(CI)和Ⅰ型断裂韧度(K_(Ic))三个属性之间的内在联系,并统计了三者之间的定量关系：TS与Cl的线性系数约等于0.075,K_(Ic)与TS的线性系数在0.1～0.15之间。这些线性关系的相关系数不高,建议每种属性采用一种试验方法获取,使结果更可靠,统计更多组试验数据,修正经验公式,为指导同类脆性岩石工程设计、评价奠定基础。
[Abstract]:The study on the fracture mechanism of brittle rocks is the basic scientific problem of deep rock engineering. The common forms of brittle rock failure include peeling, rockburst, rock burst and so on. The light damage affects the construction schedule of the engineering. The heavy losses of the casualties are caused by the heavy casualties, and the engineering failure may be induced, which concerns the national security and the national economy and the people's livelihood. The traditional test method can not explore the internal failure process of brittle rock, and the strength criterion can not effectively explain the failure of brittle rock. The classical discrete element meso model has some significant defects in the analysis of the fracture mechanism of brittle rocks. Many indoor tests and in-situ tests show that the meso tensile crack in brittle rock failure is made up. In this paper, the tensile properties of brittle rocks are studied from the angle of indoor test and meso analysis. First, a suitable meso model is selected. Secondly, the three characteristics of brittle rocks, the tensile strength of Brazil and the fracture toughness of I type, are analyzed in detail, and the mechanism of the tensile fracture of brittle rocks is investigated. The main research work and research results are as follows: (1) indoor test results of intact brittle rocks show three significant characteristics: high pressure Rabi, large internal friction angle and strength envelope nonlinear, and classical cohesive particle meso model (Bonded-particle model) - standard BPM exists these three remarkable properties in the macroscopic mechanical properties of brittle rock. Defects. By analyzing the composition and constitutive relation of the standard BPM and the characteristics of the standard BPM improved model, the reasons for these significant defects were summarized, and a new adhesive meso model (3D flat-joint model, FJM3D) was used to study the brittle rock. (2) according to the results of compression and tensile tests in Jinping marble chamber, Combining the FJM3D model checking process and the parameter sensitivity analysis results, the mesoscopic parameters that play a decisive role in the three characteristics of brittle rocks are mastered, and a set of checking methods that can comprehensively reflect the macroscopic mechanical properties of brittle rocks is proposed. (3) based on the typical Brazil splitting test and the results of the Brisbane tuff laboratory test, the polygon is used for reference. In order to approximate the circle circumference, the FJM3D model is used to generate the Brazil disc meso model directly, and the circumference resolution is used to control the circumference smoothness. The defects of the standard BPM and the problems caused by the traditional disk modeling method are solved. The key parameters of the tensile strength of the disk (BTS) are controlled by the parameter sensitivity analysis. (4) The effect of specimen size and loading rate on type I fracture toughness (K_ (Ic)) was obtained through the test of Crack chevron notched Brazilian disc (CCNBD) in the granite human shaped slot (Crack Brazilian disc, CCNBD). The microscopic model was constructed by using the FJM3D model and the smooth joint model (Smooth joint model). The relationship between the b value of the acoustic emission of the granite is about 1.7242 and the frequency of the acoustic emission events and the number of the number of cracks contained. The results show that K_ (Ic) has a linear positive correlation with the adhesive tensile strength Sigma _b, and is positively correlated with the square root of grain diameter (Davg) ~ (1/2), and the square root of the grain size (d). Max/dmin) ~ (1/2) has an exponential negative correlation. (5) looking up a large number of available brittle rock data at home and abroad, the intrinsic relationship between the tensile strength (TS), the crack initiation stress (CI) and the type I fracture toughness (K_ (Ic)) is qualitatively analyzed, and the quantitative relationship between the three ones is statistically analyzed: the linear coefficient between the TS and Cl is equal to 0.075, K_ (Ic) and TS. The linear coefficient is between 0.1 and 0.15. The correlation coefficient of these linear relationships is not high. It is suggested that each attribute is obtained by a test method to make the result more reliable, to count more experimental data and to modify the empirical formula, and to lay a foundation for guiding the design of similar brittle rock engineering and evaluation.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD315

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