单轴压缩下三维槽型裂纹扩展和连接过程的相似模型试验研究

发布时间：2018-11-20 04:55

【摘要】：在岩石力学的研究中,关于岩体内原生裂隙的启裂、扩展、连接及贯通特性一直是研究的热点与难点。对于三维裂隙岩体问题的研究,以往通常进行了二维简化,并在试验与数值模拟等方面都取得了较为系统的研究成果。但通过二维简化模型并不能全面描述多裂纹扩展与贯通过程的三维信息。为此,本文旨在通过三维裂纹相似模型试验,研究三维裂纹扩展、连接、贯通的机理及裂隙岩体的损伤断裂特性,研究结果可在岩体工程的设计、施工和稳定性分析等方面作为一定参考。为直观、清晰地观察三维裂纹的扩展、连接和贯通现象,选择了透明性良好的有机玻璃材料(PMMA)。另外,PMMA在-50℃低温下具有类似于岩石的脆性特征。为更好描述试验现象,对单轴压缩条件下几种新生裂纹的相关特征进行了统一定义,包括:翼裂纹(包裹式与劈裂式)、花瓣状裂纹、贝壳状裂纹等。本文依次设计了一根、两根、四根裂纹布置方式,且裂纹按不同角度及外端距进行布置,本文的主要结论如下:①实验过程中主要观察到了三类裂纹:翼裂纹(包裹式与劈裂式)、花斑状裂纹、贝壳状裂纹。②三维裂纹的启裂基本都出现在预制裂纹尖端,首先出现翼型裂纹,倾角较小时,裂纹启裂方向垂直于预制裂纹面;倾角较大时,启裂方向逐渐向竖直方向靠近。③裂纹的扩展形态主要受预制裂纹倾角大小的控制,A、B、C三组试样都呈现这一规律,30°布置时呈包裹式扩展,45°、60°及90°布置时呈劈裂式扩展。④随着倾角增大,试件的峰值强度逐渐降低;45°布置下,最容易出现启裂与扩展现象;裂纹倾角为0°时,出现的现象并不明显。⑤随着倾角与外端距的变化,峰值应力、启裂应力、启裂应力水平都呈现一定规律性变化,这种规律与类似二维裂纹试验所得规律基本吻合。⑥利用SPH程序进行了4根裂纹45°布置下三维裂纹启裂、扩展、连接过程的简要模拟,其扩展规律与试验现象具有一定的吻合度,但模拟得到的反翼型裂纹未能在试验中观测到。
[Abstract]:In the study of rock mechanics, the characteristics of initiation, expansion, connection and penetration of primary fractures in rock are always hot and difficult. For the study of three-dimensional fractured rock mass, two-dimensional simplification is usually carried out in the past, and more systematic research results have been obtained in the aspects of experiment and numerical simulation. However, the two-dimensional simplified model can not fully describe the three-dimensional information of the process of multi-crack propagation and penetration. Therefore, this paper aims to study the mechanism of crack propagation, connection, penetration and damage and fracture characteristics of fractured rock mass through three-dimensional crack similarity model test. The results can be used in the design of rock mass engineering. Construction and stability analysis as a certain reference. In order to observe the phenomenon of crack propagation, connection and penetration clearly and intuitively, (PMMA). With good transparency was selected. In addition, PMMA has a brittleness similar to that of rock at-50 鈩，

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