岩石断裂表面细观接触演化与剪切力学模型研究

发布时间：2017-12-31 11:12

本文关键词：岩石断裂表面细观接触演化与剪切力学模型研究　出处：《北京科技大学》2016年博士论文　论文类型：学位论文

【摘要】：岩体的抗剪强度和长期稳定性在很大程度上取决于岩石断裂粗糙面细观接触与破坏力学行为。为从细观层面探究断裂岩体粗糙表面接触状态与抗剪强度关系,采用剪切蠕变实验方法对压剪破坏和拉破坏两类断裂岩石的接触和剪切力学行为进行研究。借助激光扫描、声发射和CT检测等方法,揭示剪切过程中岩石粗糙表面凹凸体磨损过程、表面微孔洞微裂纹生长发育趋势、表面接触损伤演化等微观破坏机理以及宏观力学特征。针对岩体粗糙断裂面不连续接触的特点,提出表征断裂岩体表面接触的分形公式,建立了岩石节理的接触力学模型,为刻画和描述岩体断裂面细观接触演化过程与宏观力学行为提供了基础理论依据。论文取得的主要研究成果如下：(1)定量分析和研究了岩石断裂面形貌的细观特征。制作了压剪和拉伸两类岩石断裂面,运用激光精细扫描技术,重构了断裂岩石表面形貌：采用分形理论,对岩石断裂表面的起伏度和粗糙度进行了定量分析。(2)通过直接剪切蠕变实验,研究了断裂岩石的宏观力学行为。对断裂岩样进行分级加载剪切蠕变实验,得到了断裂岩石剪切蠕变实验中的位移、抗剪强度等,从岩样断裂面形成机制出发,揭示出两类断裂岩样在剪切蠕变条件下的宏观力学特性。(3)通过“CT切层法”,揭示了两类断裂岩石剪切蠕变破坏模式。断裂岩石在剪切蠕变作用下的破坏模式主要有：断裂面之间的剪切摩擦破坏、微小凹凸体的磨损、剪断、迁移,以及亚表面裂隙的萌生或翼裂纹发育等,展示了断裂岩石剪切蠕变前后岩石断裂面细观结构和空间展布形态、断裂岩石内部三维损伤情况。(4)利用声发射得到断裂岩石在剪切蠕变过程中和失稳前声发射频率和能量特征。拉破坏岩样的声发射能量波峰出现在蠕变中后期；压剪破坏岩样声发射能量在蠕变中期出现低谷。通过对断裂面在剪切蠕变过程中声发射定位,发现岩石断裂面声发射具带状分布特征。(5)对岩石断裂面接触区域内不同高度剖面上的接触形态分布进行厂分析。研究表明：拉破坏断裂岩样双翼接触状态呈离散“群岛式”接触,压剪断裂试样在剪切蠕变过程中接触形态为不规则“海岸式”接触。得到断裂面接触状态的变化,建立了接触面积与岩石抗剪强度的关系。(6)利用分形几何、接触力学等方法,建立丫断裂岩体在压剪载荷作用.下断裂面接触的分形模型。断裂粗糙面接触随着法向力变化产生动态演化,接触面积和接触分形维数随法向力增大而增加,压剪断裂岩样断裂面的接触多为大片起伏面之间的接触,拉破坏断裂岩样断裂面的接触多为小微凸体散点状接触。得到岩石断裂面接触过程中分形维数的变化规律,建立了压剪载荷与接触分形维数之间的关系,并由实验得到初步验证。
[Abstract]:The shear strength and long-term stability of rock mass depend to a great extent on the meso-contact and destructive behavior of rock fracture rough surface. The contact and shear mechanical behaviors of two types of fracture rocks were studied by means of shear creep test method, laser scanning, acoustic emission and CT detection. It is revealed that the wear process of the rough surface of rock during shear and the trend of the growth and development of micropores and microcracks on the surface. According to the characteristics of discontinuous contact on the rough fracture surface of rock mass, a fractal formula is proposed to characterize the surface contact of fractured rock mass. The contact mechanics model of rock joints is established. This paper provides a basic theoretical basis for describing the evolution process of mesoscopic contact and macroscopic mechanical behavior of rock fracture surface. The main research results obtained in this paper are as follows: 1). The microcosmic characteristics of rock fracture surface were quantitatively analyzed and studied. Two kinds of rock fracture surfaces, compression shear and tension, were made. The surface morphology of fractured rock was reconstructed by using laser fine scanning technique. By means of fractal theory, the fluctuation and roughness of rock fracture surface were quantitatively analyzed by means of direct shear creep experiment. In this paper, the macroscopic mechanical behavior of fractured rock is studied. The displacement, shear strength and so on in the shear creep test of fractured rock are obtained by means of graded loading shear creep experiment, and the formation mechanism of fracture surface of rock sample is discussed. The macroscopic mechanical properties of two kinds of fracture rock samples under shear creep condition are revealed. Two kinds of shear creep failure modes of fracture rock are revealed. The failure modes of fracture rock under shear creep include: shear friction failure between fracture surfaces, wear of tiny concave convex body, shear fracture and migration. As well as the initiation of sub-surface cracks or the development of wing cracks, it shows the meso-structure and spatial distribution of fracture surface before and after shear creep. Three-dimensional damage in fractured rock. The acoustic emission frequency and energy characteristics of fractured rock during shear creep and before instability are obtained by acoustic emission. The peak of acoustic emission energy of tensile failure rock appears in the middle and late period of creep. The acoustic emission energy of compression shear failure rock samples is low in the middle of creep. The acoustic emission of fracture surface is located during shear creep process. It is found that the acoustic emission of rock fracture surface has zonal distribution characteristics. The distribution of contact morphology at different heights in the contact area of rock fracture surface is analyzed in a factory. The results show that the contact state of the two wings of tensile failure rock is discrete "archipelagic" contact. The contact form of compressive shear fracture specimen is irregular "coastal" contact during shear creep, and the change of contact state of fracture surface is obtained. The relationship between contact area and shear strength of rock is established. (6) Fractal geometry, contact mechanics and other methods are used. The fractal model of contact between fracture surface and fracture surface is established. The contact area and fractal dimension increase with the increase of normal force, and the contact area and fractal dimension increase with the change of normal force. The contact of compression shear fracture rock sample fracture surface is mostly the contact between a large area of undulating surface. The contact of fracture surface of tensile failure rock sample is mostly small microconvex scattered point contact. The change rule of fractal dimension in contact process of rock fracture surface is obtained, and the relationship between compressive shear load and contact fractal dimension is established. The experimental results are preliminarily verified.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O346.1

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