裂隙几何特征对岩体力学性质及裂纹扩展规律影响的试验研究

发布时间：2018-04-06 05:29

本文选题：预置裂隙　切入点：压缩试验　出处：《中国地质大学(北京)》2015年硕士论文

【摘要】：裂隙岩体强度和变形特性受裂隙几何特征及应力条件的影响,其失稳破坏也大都是由岩体内部裂隙面的扩展、汇合贯通引起的。本文以含预置张开裂隙的纯水泥试件作为类岩石材料模拟脆性岩石,通过室内单轴压缩试验和常规三轴压缩试验,系统地研究裂隙几何特征(倾角、间距、贯通率、张开度、组数和形态)及围压对裂隙岩体力学参数的影响;同时运用Vic-3D非接触式全场应变测量系统和FLAC3D有限元数值模拟软件,分析单轴压缩条件下岩体的裂纹扩展规律。本文主要工作和研究成果如下:(1)裂隙岩体的力学特性和裂纹扩展机理分析。结合裂隙几何特征和岩体破坏过程,对裂隙岩体的力学本构模型和裂纹扩展机理进行了理论分析。(2)通过大量单轴压缩试验和部分三轴压缩试验,研究了不同裂隙几何特征及围压对裂隙试件峰值强度和弹性模量的影响。单轴压缩条件下,试件峰值强度随裂隙倾角的变化规律大致呈V型,弹性模量随裂隙倾角变化从0°到90°基本呈递增趋势,在强度最低点出现轻微回落;围压条件下,试件峰值强度和弹性模量随裂隙倾角的变化规律与单轴压缩情况类似,但强度最低点由单轴压缩时的45°变为30°。通过分析自定义的岩体力学参数折减系数随裂隙几何特征变化规律的拟合函数曲线,推测岩体力学参数对不同裂隙特征的敏感程度从大到小可作如下排列:组数间距贯通率张开度形态。从试件破坏形态来看,单轴压缩条件下试件多为脆性张拉破坏或拉剪混合破坏;在围压条件下试件均为剪切破坏,且残余强度明显增大表现出一定的塑性,其中部分试件出现二次破坏现象。(3)借助Vic-3D应变测量系统和FLAC3D数值模拟软件,分析了试件在单轴加载过程中的裂纹扩展规律。发现有拉伸裂纹、剪裂纹、翼裂纹与反翼裂纹四种形态裂纹,且以翼裂纹发育为主。裂隙尖端应力集中引起次生裂纹发育并沿近似加载方向扩展,在相邻裂隙之间或裂隙与自由面之间汇合贯通切穿岩桥,最终导致试件破坏。
[Abstract]:The strength and deformation characteristics of fractured rock mass are affected by the fracture geometry and stress conditions. The instability and failure of fractured rock mass are mainly caused by the expansion of the fracture plane and the confluence of the rock mass.In this paper, pure cement specimens with prefabricated open fissures are used to simulate brittle rocks. The geometric characteristics of fractures (inclination angle, spacing, penetration ratio, opening degree) are systematically studied by laboratory uniaxial compression test and conventional triaxial compression test.At the same time, Vic-3D non-contact full-field strain measurement system and FLAC3D finite element numerical simulation software are used to analyze the crack propagation law of rock mass under uniaxial compression.The main work and results of this paper are as follows: 1) Analysis of mechanical properties and crack propagation mechanism of fractured rock mass.Based on the geometric characteristics of fracture and the failure process of rock mass, the mechanical constitutive model and crack propagation mechanism of fractured rock mass are theoretically analyzed. (2) A large number of uniaxial compression tests and partial triaxial compression tests are carried out.The effects of different fracture geometry and confining pressure on the peak strength and elastic modulus of fracture specimen were studied.Under uniaxial compression, the variation of peak strength with crack inclination is approximately V-shaped, and elastic modulus increases with fracture inclination from 0 掳to 90 掳, and decreases slightly at the lowest point of strength, and decreases slightly under confining pressure.The variation of peak strength and modulus of elasticity with fracture inclination is similar to that of uniaxial compression, but the lowest point of strength changes from 45 掳to 30 掳under uniaxial compression.By analyzing the fitting function curve of the self-defined parameter reduction coefficient of rock mass with the geometric characteristics of fracture,It is inferred that the sensitivity of mechanical parameters of rock mass to different fracture characteristics can be arranged as follows: group number spacing penetration rate opening shape.According to the failure patterns of the specimens, most of the specimens under uniaxial compression are brittle tensile failure or tensile shear failure, but under confining pressure, the specimens are shearing failure, and the residual strength obviously increases to a certain extent of plasticity.Among them, some specimens appear secondary failure phenomenon. (3) with the help of Vic-3D strain measurement system and FLAC3D numerical simulation software, the crack propagation law of the specimen under uniaxial loading is analyzed.It is found that there are four types of cracks, namely tensile crack, shear crack, wing crack and reverse crack.The stress concentration at the crack tip leads to the development of the secondary crack and its propagation along the approximate loading direction, which leads to the failure of the specimen by connecting and cutting through the rock bridge between the adjacent cracks or between the fissure and the free surface.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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