岩石常规试验断裂损伤演化及其控制的分形几何研究

发布时间：2018-03-14 11:30

本文选题：石灰岩　切入点：损伤　出处：《山东农业大学》2014年硕士论文　论文类型：学位论文

【摘要】：岩石是由多种矿物晶粒组成的集合体,其内部结构中随机分布着大量的微裂纹和微孔隙。它不是离散介质,也不是连续介质,因此存在着宏、细观的不连续性。传统的研究方法往往把岩石均化为宏观的连续体,从而忽略了岩石材料中的微缺陷或微裂纹的形成及其发展对材料力学性能的影响。然而岩石的破坏机制是在外力作用下,其内部微裂纹萌生、扩展及贯通,直至宏观裂纹形成,促使式样破裂的整个过程。众所周知,岩石破坏后的断口记录着其断裂过程,断口上蕴藏着关于断裂机理的信息。通过对断口表面的分析可以追溯岩石断裂产生的机理。然而断口表面是粗糙不平的,其表面的几何形态难以用经典的几何语言进行描述。分形理论的研究表明：岩石断裂表面的几何形态具有分形特征,用分维数可以定量地描述岩石断口表面的粗糙程度。通过分维值可以追溯到岩石断裂时的宏观力学行为。本文利用SAW-2000微机控制电液伺服岩石三轴试验机,对鑫安煤矿所取的石灰岩试件进行一般力学性质试验,得到石灰岩单轴、三轴试验下的全应力应变曲线、岩石断口及其宏观图像。利用JSM-6510LV高低真空扫描电子显微镜,对石灰岩试件断口进行电镜扫描,获得试件断口的细观扫描图像。借助Photoshop将石灰岩断口图像处理成灰度图,利用分形理论,采用盒子计数法计算获得石灰岩断口的分形维数。从损伤力学的角度出发,根据Weibull统计分布理论,结合分形几何,在连续损伤力学的基本关系式中引入约化参数,推导出石灰岩在单轴、三轴压缩试验下的损伤模型,并与试验结果进行比较,验证了理论模型的合理性。岩石由微裂纹的萌生、发育、扩展到贯通的过程,都伴随着能量的吸收与释放。因此,从能量的角度,研究分析岩石试件断裂破坏耗散能量的分形特征,将分维值与岩石断裂的宏观特征联系起来。
[Abstract]:Rock is an aggregate composed of a variety of mineral grains, in which a large number of microcracks and micropores are randomly distributed in its internal structure. It is not a discrete medium nor a continuum medium, so there are macros. Mesoscopic discontinuities. Traditional research methods tend to transform rocks into macroscopic continuum, Therefore, the formation and development of microdefects or microcracks in rock materials have been neglected. However, the failure mechanism of rock is the initiation, propagation and penetration of internal microcracks under external force, until the formation of macroscopic cracks. The whole process of causing patterns to break. It is well known that the fracture process is recorded on the fractured surface of rock, and there is information about the fracture mechanism on the fracture surface. The mechanism of rock fracture can be traced by analyzing the fracture surface. However, the fracture surface is rough and uneven. It is difficult to describe the geometric shape of rock surface by classical geometric language. The study of fractal theory shows that the geometric morphology of rock fracture surface has fractal characteristics. The roughness of rock fracture surface can be quantitatively described by fractal dimension, which can be traced back to the macroscopic mechanical behavior of rock fracture. In this paper, SAW-2000 microcomputer controlled electro-hydraulic servo triaxial testing machine is used to test the general mechanical properties of limestone samples taken from Xinan Coal Mine, and the total stress-strain curves of limestone under uniaxial and triaxial tests are obtained. The fracture surface of limestone is scanned by electron microscope with JSM-6510LV high and low vacuum scanning electron microscope, and the meso-scanning image of fracture surface of limestone specimen is obtained. The image of limestone fracture surface is processed into grayscale image by means of Photoshop. Based on fractal theory, the fractal dimension of limestone fracture surface is calculated by box counting method. From the point of view of damage mechanics, according to the Weibull statistical distribution theory and fractal geometry, the reduced parameters are introduced into the basic relational formula of continuous damage mechanics, and the damage model of limestone under uniaxial and triaxial compression tests is derived. Compared with the experimental results, the rationality of the theoretical model is verified. The initiation, development and expansion of microcracks in rock are accompanied by the absorption and release of energy. Therefore, from the angle of energy, the fractal characteristics of energy dissipation for fracture failure of rock specimens are studied and analyzed. The fractal dimension is associated with the macroscopic characteristics of rock faults.
【学位授予单位】：山东农业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45

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